Well, restarting seems to have fixed that error message. So I guess this is solved.

Update: after trying a few things, I used the "repair online" option in Office 365, which appears to reinstall Office completely. Now the details pane in File Explorer shows additional fields, but it...

I have recently updated my desktop from Windows 7 to Windows 10. For some reason, File explorer seems unable to show metadata. For example, here is what File Explorer shows for one example powerpoint...