"could not find or load the Qt platform plugin "windows" in "",

[jrmmuller]

Dear community,

Up to recent, my windows 10 64bit laptop worked fine. However, suddently I get this error after loading certain .exe programs:

This application failed to start because it could not find or load the Qt platform plugin "windows"in "", Available platform plugins are: minimal, offscreen, windows.
Reinstalling the application may fix this problem.

I'm not a coder, I never used the Qt environment ever and other forum entries didn't help so far, since as far as I went down the rabbit hole, this is all about building code in Qt.
All I like to do is run my programs again. This error occured with multiple programs: MikTex & Texworks and converter tools. So far this error is really denying my work and I have no clue.

Thanks in advance.

Kind regards,
J. Muller

[JKSH]

@jrmmuller said in "could not find or load the Qt platform plugin "windows" in "",:

All I like to do is run my programs again. This error occured with multiple programs: MikTex & Texworks and converter tools. So far this error is really denying my work and I have no clue.

Hi @jrmmuller, the most likely cause here is that your system PATH contains a folder that contains Qt DLLs. Have you installed any new software recently or modified your PATH (shortly before this issue began)?

If I'm right, then the short version of the solution is this: You must remove the offending folder from your PATH.

(NOTE: I said "most likely". There are many possible reasons for this error).

If you do not know how to check and edit your PATH, then we can guide you through the process. However, be prepared: This will involve multiple steps -- I give you some instructions, then you carry them out and report back the details, then I give you further instructions based on what you found, then you carry them out and report back the details... iterating as many times as needed until the issue is resolved.

[koahnig]

@jrmmuller

Hi and welcome to devnet forum

You are right and it is a Qt related issue.

However, the problem is with an application using Qt and therefore, they are probably the only devs being able to you.
The problem I see is that they have used a particular version of Qt and part of your installation may have been corrupted by whatever reason.

The Programs you are listing are probably all from the same open source project and tex related.

I have MikTex and stuff installed as well, but even though I am a developer and know parts of Qt application development, I would go the route and check the MikTex forum and eventually reinstall MikTex again.

[jrmmuller]

@koahnig Hi Koahnig,

Thanks for your response. Actually it is partly for MikTex, the conversiontools are for converting photo files.

I tried installing and reinstalling Miktex and trying Texlive, but that didn't help unfortunately.

[jrmmuller]

@JKSH said in "could not find or load the Qt platform plugin "windows" in "",:

@jrmmuller said in "could not find or load the Qt platform plugin "windows" in "",:

All I like to do is run my programs again. This error occured with multiple programs: MikTex & Texworks and converter tools. So far this error is really denying my work and I have no clue.

Hi @jrmmuller, the most likely cause here is that your system PATH contains a folder that contains Qt DLLs. Have you installed any new software recently or modified your PATH (shortly before this issue began)?

If I'm right, then the short version of the solution is this: You must remove the offending folder from your PATH.

(NOTE: I said "most likely". There are many possible reasons for this error).

If you do not know how to check and edit your PATH, then we can guide you through the process. However, be prepared: This will involve multiple steps -- I give you some instructions, then you carry them out and report back the details, then I give you further instructions based on what you found, then you carry them out and report back the details... iterating as many times as needed until the issue is resolved.

Hi JKSH,

OK, that sounds as that might be the case. Unfortunately I don't know how to edit the path or which could be the cause that modified the PATH. I'm not sure which applications I've installed since the error began.

If you could help me with the steps, that would be great!

KR,

[VRonin]

@jrmmuller said in "could not find or load the Qt platform plugin "windows" in "",:

If you could help me with the steps

Open cmd and type echo %QT_PLUGIN_PATH% if it's not empty then delete it (just google: delete environmental variable windows #, where # is your windows version)

Open cmd and type echo %PATH% and press enter. You'll see a list separated by ; of folder paths. Go line by line and make sure they do not point to a folder that contains a platforms folder that has qwindows.dll in it. If you find such a path edit the PATH variable and remove it (just google: edit environmental variable windows #, where # is your windows version)

[JKSH]

What version of MiKTeX are you using?

@jrmmuller said in "could not find or load the Qt platform plugin "windows" in "",:

If you could help me with the steps, that would be great!

1. Download ListDLLs from https://docs.microsoft.com/en-us/sysinternals/downloads/listdlls
2. Extract the contents of the zip file into C:\ListDLLs
3. Try to launch MiKTeX. When the error dialog appears ("Could not find or load..."), leave it open; don't close the dialog.
4. Press Windows+R (this launches the "Run" window)
5. Type "cmd" into the "Run" window and press Enter (this launches the Command Line, cmd, that @VRonin mentioned)
6. In cmd, type cd C:\ListDLLs and press Enter
7. In cmd, type ListDLLs.exe miktex and press Enter. You should see a long list of DLLs.
8. In cmd, type ListDLLs.exe miktex > output.txt and press Enter. You should see a new text file.
9. Open C:\ListDLLs\output.txt and copy+paste its contents here in this forum.
10. You can close the error dialog now.
11. In cmd, type echo %QT_PLUGIN_PATH% and press Enter. What gets shown after that? Write it here in this forum. (this is related to @VRonin's suggestion)

[jrmmuller]

@VRonin

Hi VRonin,

I followed your steps and looked up the environmental variable. It turns out that the %Qt_Plugin_path% was indeed set by a certain program (numerical model) which I had installed. I deleted the variable and rebooted the system. As a result all the programs were functioning again without errors.

Considered this solved. Thanks a lot!

[jrmmuller]

@JKSH
Hi JKSH, I appreciate your help. Thanks to your help and VRonin, my issue has been resolved.

Kind regards.

[KKekana]

@JKSH Your steps seem useful. However, I am working on pyzo. So I replaced all the words with 'miktex' with 'pyzo' (I'm amateur at coding as well). The cmd window spat out a long list of DLLs and the txt file was created after step 8.

However, I am not sure what you mean by copy and paste the contents 'here' in step nine.

I copied the text file info to the cmd window, but the programme says "....is not recognized as an internal or external command, operable program or batch file".

Not sure how to continue from here. Thanks

[JKSH]

@KKekana said in "could not find or load the Qt platform plugin "windows" in "",:

However, I am not sure what you mean by copy and paste the contents 'here' in step nine.

I've updated the post to clarify: Copy + paste its contents in this forum

[HZMD]

I notice this thread - which I found searching the error msg in Google - just kind of died without coming to a resolution others could follow.

JKSH - I'm having the same issue with several programs. I'm not sure what I installed that did the damage, but I suspect it might be drivers for a pen display. I followed the steps you listed, but instead of for Krita, an open source paint program I use for testing. The following big list is what was in the output. I see several instances of QT in there, but I'm not sure what to do from there.

//krita.exe pid: 39352
Command line: "C:\Program Files\Krita (x64)\bin\krita.exe" 

Base                Size      Path
0x0000000040000000  0xfc3000  C:\Program Files\Krita (x64)\bin\krita.exe
0x000000000b450000  0x1ed000  C:\WINDOWS\SYSTEM32\ntdll.dll
0x000000000b230000  0xb3000   C:\WINDOWS\System32\KERNEL32.DLL
0x0000000007710000  0x293000  C:\WINDOWS\System32\KERNELBASE.dll
0x000000000af10000  0x9e000   C:\WINDOWS\System32\msvcrt.dll
0x00000000c9a60000  0x39000   C:\Program Files\Krita (x64)\bin\libkritaglobal.dll
0x00000000b9600000  0x121000  C:\Program Files\Krita (x64)\bin\libkritawidgetutils.dll
0x0000000061440000  0x1a000   C:\Program Files\Krita (x64)\bin\libgcc_s_seh-1.dll
0x000000006fc40000  0x164000  C:\Program Files\Krita (x64)\bin\libstdc++-6.dll
0x00000000c9a00000  0x5c000   C:\Program Files\Krita (x64)\bin\libKF5ConfigCore.dll
0x000000000ac40000  0x197000  C:\WINDOWS\System32\USER32.dll
0x00000000c7a20000  0x56000   C:\Program Files\Krita (x64)\bin\libKF5I18n.dll
0x00000000076f0000  0x20000   C:\WINDOWS\System32\win32u.dll
0x00000000b0be0000  0xc28000  C:\Program Files\Krita (x64)\bin\libkritaui.dll
0x000000000a880000  0x29000   C:\WINDOWS\System32\GDI32.dll
0x0000000007c90000  0x19a000  C:\WINDOWS\System32\gdi32full.dll
0x0000000007650000  0xa0000   C:\WINDOWS\System32\msvcp_win.dll
0x0000000007b90000  0xfa000   C:\WINDOWS\System32\ucrtbase.dll
0x00000000ac770000  0x5a9000  C:\Program Files\Krita (x64)\bin\Qt5Gui.dll
0x00000000b0360000  0x5d2000  C:\Program Files\Krita (x64)\bin\Qt5Core.dll
0x000000000a600000  0x155000  C:\WINDOWS\System32\ole32.dll
0x0000000008a10000  0xa3000   C:\WINDOWS\System32\ADVAPI32.dll
0x0000000008680000  0x32d000  C:\WINDOWS\System32\combase.dll
0x0000000092400000  0x576000  C:\Program Files\Krita (x64)\bin\Qt5Widgets.dll
0x000000000a760000  0x9e000   C:\WINDOWS\System32\sechost.dll
0x000000000afb0000  0x122000  C:\WINDOWS\System32\RPCRT4.dll
0x0000000009110000  0x14f0000  C:\WINDOWS\System32\SHELL32.dll
0x0000000007520000  0x7e000   C:\WINDOWS\System32\bcryptPrimitives.dll
0x0000000007e30000  0x4a000   C:\WINDOWS\System32\cfgmgr32.dll
0x000000000b190000  0x6d000   C:\WINDOWS\System32\WS2_32.dll
0x00000000c96d0000  0x3b000   C:\Program Files\Krita (x64)\bin\Qt5Xml.dll
0x000000000b0e0000  0xa8000   C:\WINDOWS\System32\shcore.dll
0x0000000007ea0000  0x74a000  C:\WINDOWS\System32\windows.storage.dll
0x00000000c78d0000  0x93000   C:\Program Files\Krita (x64)\bin\libkritaodf.dll
0x00000000edf90000  0x23000   C:\Program Files\Krita (x64)\bin\libkritaplugin.dll
0x0000000007450000  0x24000   C:\WINDOWS\System32\profapi.dll
0x0000000064940000  0x15000   C:\Program Files\Krita (x64)\bin\libwinpthread-1.dll
0x00000000074c0000  0x5d000   C:\WINDOWS\System32\powrprof.dll
0x00000000090b0000  0x52000   C:\WINDOWS\System32\shlwapi.dll
0x0000000007480000  0x11000   C:\WINDOWS\System32\kernel.appcore.dll
0x00000000d9810000  0x29000   C:\Program Files\Krita (x64)\bin\libKF5ConfigGui.dll
0x00000000c7140000  0x8b000   C:\Program Files\Krita (x64)\bin\libKF5CoreAddons.dll
0x00000000d6c80000  0x29000   C:\Program Files\Krita (x64)\bin\libKF5GuiAddons.dll
0x0000000007e80000  0x17000   C:\WINDOWS\System32\cryptsp.dll
0x00000000c7c60000  0x3d000   C:\Program Files\Krita (x64)\bin\libKF5ItemViews.dll
0x00000000d6b30000  0x2d000   C:\Program Files\Krita (x64)\bin\libKF5WindowSystem.dll
0x00000000b6b70000  0x12a000  C:\Program Files\Krita (x64)\bin\libKF5WidgetsAddons.dll
0x00000000c77e0000  0x5a000   C:\Program Files\Krita (x64)\bin\Qt5PrintSupport.dll
0x000000000a8b0000  0x127000  C:\WINDOWS\System32\comdlg32.dll
0x00000000da5f0000  0x1e000   C:\Program Files\Krita (x64)\bin\libintl.DLL
0x00000000f1d80000  0xe000    C:\Program Files\Krita (x64)\bin\libkritacolor.dll
0x00000000d4aa0000  0x1e000   C:\Program Files\Krita (x64)\bin\libkritacommand.dll
0x00000000af0b0000  0x4a2000  C:\Program Files\Krita (x64)\bin\libkritaimage.dll
0x00000000c99d0000  0x21000   C:\Program Files\Krita (x64)\bin\libkritaimpex.dll
0x00000000b4370000  0x209000  C:\Program Files\Krita (x64)\bin\libkritaflake.dll
0x00000000c6e10000  0x69000   C:\Program Files\Krita (x64)\bin\libkritalibbrush.dll
0x00000000ce300000  0x1e000   C:\Program Files\Krita (x64)\bin\libkritastore.dll
0x00000000f0aa0000  0xe000    C:\Program Files\Krita (x64)\bin\libkritaversion.dll
0x00000000b52d0000  0x1d1000  C:\Program Files\Krita (x64)\bin\libkritapigment.dll
0x00000000c3450000  0x5a000   C:\Program Files\Krita (x64)\bin\libkritapsd.dll
0x00000000c7490000  0x3c000   C:\Program Files\Krita (x64)\bin\libKF5Completion.dll
0x00000000b6a70000  0xfb000   C:\Program Files\Krita (x64)\bin\libkritawidgets.dll
0x00000000b2f60000  0x264000  C:\Program Files\Krita (x64)\bin\libexiv2.dll
0x000000000b220000  0x8000    C:\WINDOWS\System32\PSAPI.DLL
0x00000000c3410000  0x3e000   C:\Program Files\Krita (x64)\bin\libpng16.dll
0x00000000a6ab0000  0xf1000   C:\Program Files\Krita (x64)\bin\Qt5Multimedia.dll
0x00000000a6970000  0x132000  C:\Program Files\Krita (x64)\bin\Qt5Network.dll
0x00000000bb6d0000  0x4e000   C:\Program Files\Krita (x64)\bin\libHalf.dll
0x0000000005ea0000  0x2e000   C:\WINDOWS\SYSTEM32\dwmapi.dll
0x00000000079b0000  0x1db000  C:\WINDOWS\System32\CRYPT32.dll
0x00000000fc8d0000  0x1a000   C:\WINDOWS\SYSTEM32\MPR.dll
0x0000000002e10000  0xa000    C:\WINDOWS\SYSTEM32\VERSION.dll
0x00000000074a0000  0x12000   C:\WINDOWS\System32\MSASN1.dll
0x00000000fbd30000  0x24000   C:\WINDOWS\SYSTEM32\WINMM.dll
0x00000000fe370000  0x17000   C:\WINDOWS\SYSTEM32\NETAPI32.dll
0x0000000007350000  0x28000   C:\WINDOWS\SYSTEM32\USERENV.dll
0x0000000005860000  0x9c000   C:\WINDOWS\SYSTEM32\UxTheme.dll
0x00000000c9970000  0x12000   C:\Program Files\Krita (x64)\bin\iconv.dll
0x00000000e8ec0000  0xa9000   C:\WINDOWS\WinSxS\amd64_microsoft.windows.common-controls_6595b64144ccf1df_5.82.17763.379_none_10e5882c642d5588\COMCTL32.dll
0x00000000fd890000  0x89000   C:\WINDOWS\SYSTEM32\WINSPOOL.DRV
0x00000000085f0000  0x26000   C:\WINDOWS\System32\bcrypt.dll
0x00000000a6860000  0x10f000  C:\Program Files\Krita (x64)\bin\libfftw3.dll
0x00000000f0170000  0x10000   C:\Program Files\Krita (x64)\bin\Qt5Concurrent.dll
0x00000000ba1c0000  0x52000   C:\Program Files\Krita (x64)\bin\Qt5Svg.dll
0x00000000c3310000  0x2d000   C:\Program Files\Krita (x64)\bin\libKF5Archive.dll
0x00000000b9900000  0x35000   C:\Program Files\Krita (x64)\bin\libexpat.dll
0x00000000c94f0000  0x1f000   C:\Program Files\Krita (x64)\bin\libzlib.dll
0x0000000006a70000  0xc6000   C:\WINDOWS\SYSTEM32\DNSAPI.dll
0x0000000006a30000  0x3d000   C:\WINDOWS\SYSTEM32\IPHLPAPI.DLL
0x000000000a810000  0x8000    C:\WINDOWS\System32\NSI.dll
0x00000000fbd00000  0x2d000   C:\WINDOWS\SYSTEM32\WINMMBASE.dll
0x0000000003fb0000  0x1a8000  C:\WINDOWS\SYSTEM32\PROPSYS.dll
0x000000000ade0000  0xcb000   C:\WINDOWS\System32\OLEAUT32.dll
0x0000000006b40000  0xe000    C:\WINDOWS\SYSTEM32\NETUTILS.DLL
0x0000000002930000  0x3f000   C:\WINDOWS\SYSTEM32\LOGONCLI.DLL
0x0000000002010000  0x18000   C:\WINDOWS\SYSTEM32\SAMCLI.DLL
0x000000000b3f0000  0x2e000   C:\WINDOWS\System32\IMM32.DLL
0x0000000008ac0000  0x16a000  C:\WINDOWS\System32\MSCTF.dll
0x00000000df550000  0x15b000  C:\Program Files (x86)\Stardock\Launch\Launch8_64.dll
0x00000000048e0000  0x5be000  C:\WINDOWS\SYSTEM32\d2d1.dll
0x00000000ef6e0000  0x2c0000  C:\Program Files (x86)\Stardock\Start10\Start10_64.dll
0x00000000ef4f0000  0x114000  C:\Program Files (x86)\Stardock\ShadowFX\ShadowFX_64.dll
0x00000000a6430000  0x153000  C:\Program Files (x86)\Stardock\Fences\FencesMenu64.dll
0x0000000003200000  0x13000   C:\WINDOWS\SYSTEM32\WTSAPI32.dll
0x00000000fd420000  0x1a5000  C:\WINDOWS\WinSxS\amd64_microsoft.windows.gdiplus_6595b64144ccf1df_1.1.17763.379_none_36a32ecd61af0e6f\gdiplus.dll
0x00000000eee70000  0x95000   C:\WINDOWS\System32\TextInputFramework.dll
0x00000000ee8e0000  0x322000  C:\WINDOWS\System32\CoreUIComponents.dll
0x00000000054e0000  0xe2000   C:\WINDOWS\System32\CoreMessaging.dll
0x0000000006510000  0x31000   C:\WINDOWS\SYSTEM32\ntmarta.dll
0x0000000003800000  0x153000  C:\WINDOWS\SYSTEM32\wintypes.dll
0x00000000fbff0000  0x6c000   C:\WINDOWS\system32\Oleacc.dll

It may also be of interest that when I tried the "echo %QT_PLUGIN_PATH%" step, it just echoed "%QT_PLUGIN_PATH%" on it's own line. Also, when I tried the process with another program name with the same problem - Medibang Paint Pro, with the executable named "MediBangPaintPro.exe" as C:\ListDLLs>ListDLLs.exe MediBangPaintPro or MediBangPaintPro.exe it returns "No matching processes were found."

Thanks in advance, if you're still in the mood to look into this. :)

[JKSH]

@HZMD said in "could not find or load the Qt platform plugin "windows" in "",:

I notice this thread - which I found searching the error msg in Google - just kind of died without coming to a resolution others could follow.

The OP's (@jrmmuller) problem was resolved. In their case, the %QT_PLUGIN_PATH% variable was hijacked by another program so the variable had to be cleared

@KKekana was a different user.

when I tried the "echo %QT_PLUGIN_PATH%" step, it just echoed "%QT_PLUGIN_PATH%" on it's own line.

This is good. It shows that the %QT_PLUGIN_PATH% variable has not been hijacked by another program. It means the root cause of your problem is different from the OP.

I'm having the same issue with several programs. I'm not sure what I installed that did the damage, but I suspect it might be drivers for a pen display.

Do all of these programs use Qt? Does the pen display driver use Qt?

Also, how did you install Krita? Does uninstalling + reinstalling it help?

The following big list is what was in the output.

2 things stood out to me:

1. qwindows.dll is missing. Can you see if it's on your system somewhere? I'd expect it to be at C:\Program Files\Krita (x64)\bin\platforms\qwindows.dll (unless Krita's developers did something different)
2. Krita is loading DLLs from C:\Program Files (x86)\Stardock\ -- is this expected? What happens if you temporarily rename the Stardock folder; does Krita load properly then?

[HZMD]

Do all of them use Qt? - I'm not sure, and I'm not sure how to find out.

How did I install Krita? - It would be non-helpful if I said "in the normal way" wouldn't it? I'm definitely not a proper programmer, though I'm "programmer adjacent" in some aspects of my work, learning enough from programmers to describe it to non-programmers in pictures. Anyway, I downloaded an executable installer from Krita.org and let it do its thing. Is that the right information?

Does uninstalling and reinstalling help? - On the others I have encountered this problem with, it has. I haven't done Krita yet, because I was hoping to find the original culprit, and thought there might be clues.

qwindows.dll is missing - Hey, I think Krita uses Qt! I found qwindows.dll in C:\Program Piles\Krita (x64)\bin\platforms

Using that newfound knowledge, I looked for it in Autodesk Sketchbook and MediBang Pro (other programs this has happened with) and found it in C:\Program Files\Autodesk\Sketchbook\platforms and C:\Program Files\Medibang\Medibang Paint Pro\platforms

I also looked for "qwindows" in the "program files" and "program files (x86) folders and found it in the folders of:

• MeshLab (Same error when I try to launch it - that means it's not the culprit, right?)
• Logitech Gaming Software (I use a gaming mouse because it has lots of assignable buttons)
• Hamstersoft ZIP Archiver (which is Russian and scary as hell, but does a really good job)
• Allgorithmic Substance painter, Substance Designer, and Substance Player
• Several Photoshop plugins by Alien Skin (iirc, that may have been the first thing that threw this error, but they've been reinstalled)
• Autodesk Mudbox
• Adobe Bridge
• Explorer actually crashed once while doing this, and it still claims to be searching the program files folder - I'll come back and edit this with any others it finds, or that it finds in Program Files (x86)

I did not find qwindows in the folder of the pen display driver / control software I suspected of having monkeyed things up. Am I right in thinking that means that driver / control software is innocent? With no more evidence than I had before, I now suspect Logitech. I'm sure this is how witch trials get started. ;)

[HZMD]

Logitech suffers the same error on reboot, when it's executable "LCore" can't find the windows (qwindows?) platform plugin that is, in fact, in the platform folder. So I guess they're innocent, too, right?

The other question asked - if it was expected for Krita to access Stardock - I guess so? Stardock makes Windows modification software, to change the look and behaviors of windows, menus, the desktop, icons, etc. So I guess Krita is getting instructions for things like menu animations.

[JKSH]

@HZMD said in "could not find or load the Qt platform plugin "windows" in "",:

Do all of them use Qt? - I'm not sure, and I'm not sure how to find out.

In general, you check for the presence of Qt DLLs (Qt5Core.dll, qwindows.dll) in the program's folders.

How did I install Krita? - It would be non-helpful if I said "in the normal way" wouldn't it? I'm definitely not a proper programmer, though I'm "programmer adjacent" in some aspects of my work, learning enough from programmers to describe it to non-programmers in pictures. Anyway, I downloaded an executable installer from Krita.org and let it do its thing. Is that the right information?

Yes, that's the right information :) Other possible ways to install Krita include "compile it from source".

Anyway, since you used the "normal way", that rules out the possibility of the error being caused by incorrect installation/compilation/deployment

Does uninstalling and reinstalling help? - On the others I have encountered this problem with, it has. I haven't done Krita yet, because I was hoping to find the original culprit, and thought there might be clues.

From the symptoms you've described and the ListDLLs output you posted, I can't see an easy way to find the root culprit, unfortunately.

The easiest thing to do might be to reinstall the affected software and move on with your life.

One other thing you could try: If you create a new user account on your PC, does that account manage to run the affected programs normally? If it does, that means something has gone wrong in your current Windows account itself. (I can't explain how though)

qwindows.dll is missing - Hey, I think Krita uses Qt! I found qwindows.dll in C:\Program Piles\Krita (x64)\bin\platforms

Using that newfound knowledge, I looked for it in...

...I'll come back and edit this with any others it finds, or that it finds in Program Files (x86)

That's OK, you don't have to give us a comprehensive list.

I asked about other Qt-based software because sometimes, problems occur when a piece of Qt-based software adds itself to the system-wide PATH (or QT_PLUGIN_PATH). This can cause other Qt-based software to load the wrong version of Qt DLLs.

However, given that you can repair individual programs by re-installing them, that probably means your problem is caused by something else.

I did not find qwindows in the folder of the pen display driver / control software I suspected of having monkeyed things up. Am I right in thinking that means that driver / control software is innocent? With no more evidence than I had before, I now suspect Logitech. I'm sure this is how witch trials get started. ;)

It is difficult to prove that someone/thing didn't do it.

[fcarney]

@HZMD said in "could not find or load the Qt platform plugin "windows" in "",:

I'm sure this is how witch trials get started. ;)

Double double toil and trouble...

But seriously if you want to find the culprit you have to see if it floats. So measure it against other things that float. Like ducks, wood, and tiny tiny pebbles.

(Apologies in advance for my complete disdain for seriousness in this serious topic. Far too much silliness in my post.)

[HZMD]

@JKSH said:

Other possible ways to install Krita include "compile it from source".

I knew that one! Or, I knew that was a thing, in an abstract, not-something-I-know-how-to-do way ;)

@JKSH said:

I can't see an easy way to find the root culprit, unfortunately.

Ah... This gives me a sad. It would be somehow satisfying to be able to say "Ah ha! It's your fault, you little..." but, alas... Moving on is, as you say, the best course of action if that's not possible.

Thank you for your help and patience. :)

[HZMD]

@fcarney said in "could not find or load the Qt platform plugin "windows" in "",:

So measure it against other things that float. Like ducks, wood, and tiny tiny pebbles.

This new learning amazes me... Do you know of a way sheep's bladders may be employed to prevent earthquakes?

[LukeMax_Li]

I solved it:
add system environment
QT_QPA_PLATFORM_PLUGIN_PATH
C:\Qt\Qt5.12.2\5.12.2\msvc2017_64\plugins\platforms