Libre Office spreadsheet being corrupted

I have just done a clean reinstallation of Windows and Libre Office, and my spreadsheet are being corrupted. I entered data on Tuesday and Wednesday, but when I came back to the spreadsheets on Thursday and today Friday they are all corrupted. When I open a file I am presented with a blank page which does not respond to any input from the keyboard or mouse. I can’t even use the mouse to exit; I have to use Ctrl-Alt-Del.
Any ideas?

SJF

The installation is correct? Try restarting LibreOffice in Safe Mode (menu Help).
Are your disk files corrupted? Try to open a file from a removable device.

Maybe Windows has been updating and needs restarting. It normally takes several restarts and waits while it evaluates, downloads and installs dependent updates. Some update installs affect LibreOffice ability to run until PC has restarted.

I always shutdown fully (turn off fast start) Windows computer overnight as it gives it a chance to sort itself out.

Does it mean you don’t see anything? Is some kind of dark theme active? If so, does it behave the same under a light theme?