Hello LASB30,
Thank you for posting in the Apple Support Communities. I understand that you’re seeing an error prompt when using Font Book. You also have a question about Font Book compatibility with third-party software. I’d like to assist.
First, I recommend reaching out to Microsoft to see if Font Book is compatible with Parallels.
As for the error message you’re seeing, I suggest taking each of these steps to install and validate fonts on your Mac: Install and validate fonts in Font Book on Mac
If the issue persists, boot your Mac into safe mode or log into a new user account to see if the issue happens there:
Use safe mode to isolate issues with your Mac
How to test an issue in another user account on your Mac
I hope this information is useful. Kind regards.