Hello XXXYYYY290,
You can use the steps below to reinstate the backup of your library that was made before starting the repair process:
1. If the Photos app
on your Mac is open, choose Photos > Quit Photos.
2. Click the Time Machine icon in the menu bar and choose Enter Time Machine, or choose Apple menu
> System Settings, click General in the sidebar, then click Time Machine
on the right. (You may need to scroll down.)
3. Time Machine opens and shows your available backups.
4. Click the date of your last backup, navigate to the backup of your photo library, then click to select it.
5. Click Restore.
6. Depending on the size of your library, it may take some time for your library to be restored. When you next open Photos, you should be able to use your Photos library as it was when last backed up.
You can also find those steps in the resources below:
Restore a library from Time Machine in Photos on Mac - Apple Support
Repair your library in Photos on Mac - Apple Support
Should you still be unable to open your photos library, or sync with iCloud, you'll want to reach out to Apple Support: Apple Support They'll be in the best position to look into this further.
Take care.