word 2016 can't save document

I have a MacBook air from 2015 and as of this morning I have not been able to save my Word documents (Word 2016). I've never had issues before.

When I press save on a new document, a message pops up saying, "The file “Documents” couldn’t be opened." Why is this happening?

Sounds like you haven't granted Word permission to access your ~/Documents folder. Check in System Preferences > Security & Privacy > Privacy tab and see if Microsoft Word is listed in the Files and Folders section with any unchecked items. You can also try adding it to the Full Disk Access area.

If that doesn't work, you might be looking at a more general permissions problem with your Home folder. In that case https://support.apple.com/en-us/HT203538 is worth checking out. Good luck!