Pictures are scanned when they are imported, and they are never scanned again. Waiting, switching things on and off, or cursing won't change that. I know this.
But I understand that you're importing new pictures, and they aren't being scanned? How do you add the pictures? If you don't use File>Import or other normal processes, then the pictures might not get scanned when they are added. If you're not sure, then try adding new pictures to Finder folders, and then using File>Import rather than going directly into Photos.
If you haven't already, you should try these things to help narrow things down:
- Restart the computer (of course)
- Re-start in Safe Mode. This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this:
Start up your Mac in safe mode - Apple Support
- Use another library if you have one, or make a small test Library with a few pictures in it and see if the same thing happens. You can create a new Library by closing Photos and then option-clicking on the Photos icon.
- Make a new user and see if the same problem recurs with it. This is a bit harder, because a new user can't access a different user's stuff. You would need to move your Library out of your own user's folder up to the general "Users" folder.
- Rebuild your Photos Library--close Photos and re-launch by option-command-clicking the app icon. I put this last, because if you're using iCloud Photos to synchronize with iCloud, then re-syncing may take quite a long time.
The idea is to find out if the problem is with the Library, with your account, or with caches and login items, and stuff like that. One of these steps may fix the problem, but their failure to work also helps figure out what's happening.
Let us know what happens…
