How large is your Photos Library /Users/robertarchibald/Pictures/Photos Library.photoslibrary?
Rebuilding a large library may take several hours and you need plenty of free storage on the volume with the library. You must not interrupt Photos while it is rebuilding the library, or the library may get damaged. Let it run.
If Photos cannot rebuild the library even after waiting a day or two, you may want to restore an older version of your Photos Library from your Time Machine backup to your Pictures folder.
Or have you been using iCloud Photos? If your Photos Library is in iCloud, the easiest way to restore a working version of your Photos Library would be to
- Quit Photos, then save your current library /Users/robertarchibald/Pictures/Photos Library.photoslibrary on an external drive to keep a backup copy of it, so you can recover your photos from it, if all should fail.
- Remove the old Photos Library from your Mac, if you do not have enough free storage for another copy.
- Now create a new, empty Photos Library and make it the System Photos Library and enable iCloud Photos again.
- Wait for your photos to come back from iCloud.