Tried repair too. No change.
I must be a 1-of-1 with my issue. I've installed and reinstalled about 30 times. Different versions. Tried 7.0.
Always kept Calibre up to date for years on the same laptop. Never had any issues until a few weeks ago.
Updated the graphics driver to the latest 2023 version. Added the QT Env Variable.
Only thing that works is reverting back to 32-bit version 5.44.
Just to show you one aspect of the behavior. The below screenshot shows that when I hover over the taskbar app, it appears as a white window, but if I click on it nothing happens. So it's there, but won't bring up the window.
