I'm seeing in the Preferences -> Sync that I cannot use Dropbox for macOS on FIle Provider on one of my computers. I'm trying to figure out why it works on some computers and not others.
The message says:

Following the "Learn more" link leads me to an article that points out that Photos libraries, Final Cut projects and Logic Pro projects can't be synced with File Provider.
But, I don't think I have any of those. The closest I come is a directory named "Photos" but it is not a Photos Library.
Also, that directory appears on other computers with very similar specs (OS, architecture) to the machine in question. But, those computers use File Provider just fine.
Any hints? How can I determine which files it is complaining about?