[Interest] Qt permanently broke on computer

[Jason H]

> I tried to port an app on a Win10 PC. That went well. Then I tried to deploy (windeployqt) it.
>
> Now when I run it in creator I get:
> 10:26:28: Starting C:\Users\Admin\Projects\build-phidget-spinner-Desktop_Qt_5_15_2_MinGW_64_bit-Debug\debug\phidget-spinner.exe ...
> qt.qpa.plugin: Could not find the Qt platform plugin "windows" in ""
>
> I have deleted the C:\Qt dir and re-installed.
> I have cleaned the app source dir and deleted the shadow build dirs, deleted the .pro.user file,
> I launched QtC from the start menu.
>
> I have no idea how to get this working again.

Some additional info:
Other projects work.
The crash is in this statement:
QGuiApplication app(argc, argv);

the stack indicates a crash starting at:
QGuiApplicationPrivate::createPlatformIntegration()


All the online help (stackexchange) seems to be about deployment, but I'm just trying to run it in creator.