Some export operations not performed. An unknown error occurred

Recently had a problem exporting files to my hard drive. I'm getting an error message:

Some export operations not performed. An unkown error occurred.

I've restarted my PC a couple of times. I've tried exporting to an external drive. I've tried exporting via email

All got the same error message

I'm using Lightroom Classic 11.3.1 and Windows 10