The GUI is not displayed on the screen.
When I run my program in Debug or Release mode, my GUI is not displayed on the screen, but if I run my Task Manager (Ctrl + Alt + Del) I see that my (exe) is running.
What intrigues me is that everything was working normally, and suddenly appeared this problem.
Somebody help me, please.
If working normally means that the GUI was being displayed prior to some change, try undoing parts of the change piece by piece until it works again. If not working is frustrating, you can also reverse the order and go from a working program forward until it breaks.
Alternatively, can we get some more information such as the Qt version, OS, and a small example that demonstrates the issue?