[timnz]

Here's the output from the debugger:

Spoiler:

Turning on automatic hidpi scaling
devicePixelRatio: 1.0
logicalDpi: 96.0 x 96.0
physicalDpi: 95.8113948919 x 95.9160839161
Using calibre Qt style: True
Qt WebEngine resources not found at C:/Program Files/Calibre/app/resources. Trying parent directory...
Qt WebEngine resources not found at C:/Program Files/Calibre/app. Trying application directory...
Qt WebEngine resources not found at C:/Program Files/Calibre. Trying fallback directory... The application MAY NOT work.
[0916/132550.340:ERROR:icu_util.cc(170)] Invalid file descriptor to ICU data received.

Originally Posted by JSWolf

One other thing to try is to uninstall Calibre and reinstall. Also, rename your Calibre configuration directory to Calibre.bak and also make a copy of it.

The configuration directory is in %appdata% and the directory is Calibre.

I'll try this next.