QML Form Editor/Designer shows empty rectangle in place of an item

[Sunita Marshal]

I'm new to Qt.
I'm currently on Windows 7 ESU with Qt v5.15.2 and Qt Creator v4.14.0 installed.
Under Qt Creator -> Form Editor for QML ui file, when I drag items to my form, they are just empty rectangles - not like the real shape of the items as shown in the following official Qt tutorial video:

https://youtu.be/GkzncJ71mm0?t=41

Even when I set their color and other properties, they are not reflected in design mode. However the text editor reflect them right away. Also when the app is built and run, it works fine and shows exactly what we design.

The tutorial video is from 2018 and then obviously some old version of Qt Creator was used. I doubt this live form/item editing support in Qt Creator might be dropped in later versions for some technical reasons. Am I right?

If not, how can I get that live editing of QML forms enabled in my Qt Creator v4.14.0?

[Sunita Marshal]

I uninstalled and reinstalled Qt Creator but nothing changed.

[Sunita Marshal]

Any solution to my problem...???