Mac Photos app will no longer import photos
Been transferring old photos from a backup hard drive into the MacOS Photos app. Was working fine, then suddenly stopped working, although both iCloud and local drive have plenty of storage and I'm importing from the same drive that worked before. No error, message, the app lets me click "import new photos", and then nothing happens and the photos aren't imported. I tried re-booting, which has fixed a similar problem in the past (a problem which at least gave me an error message to let me know the photos weren't imported), but no luck this time.
Any suggestions would be very welcome!
MacBook Air 13″