Unable to access anything: 4.0.1 running Windows 11

Help please! I installed MuseScore 4 a couple of days ago and wrote out a score using it. Found one bug, which was that I couldn't add a measure using the Add menu, but could using the option down the left side. Downloaded 4.0.1 yesterday and opened up a file OK. However, this morning, having gone out of the file and renamed a different one that was created in 4.0.0, it wouldn't open up anything and was completely dead. I had to go into Task Manager to close the program.

I tried uninstalling and reinstalling 4.0.1 and got a message telling me that the software couldn't be configured. No idea why... However, the icon appeared on my desktop!? Clicked on it and attempted to open the file again - still not working.

So what now?