Catalina Photo Library Error

Howdy JillTubaugh,

Thanks for using the Apple Support Communities! I understand that you are unable to open a photos library after updating your software. Let’s take a look and see what we can do. I'm happy to help!

Let's test booting your Mac up in Safe Mode. If it works in safe mode please reboot the computer again and see if it works in the normal user environment.

Use safe mode to isolate issues with your Mac

"How to use safe mode"

1. Turn on or restart your Mac, then immediately press and hold the Shift key as your Mac starts up.
2. Release the key when you see the login window. ”Safe Boot” should appear in the upper-right corner.
3. Log in to your Mac. 

If you continue to have issues with Photos on Mac please Contact Apple Support for more assistance. 

Best regards!

Apple doesn't support storing your Photos Library on a network-accessed drive. They never have, but people have gotten away with it (or failed to notice it not working correctly). Now in Catalina it just seems not to work.

Another no-go is the Time Capsule. The new security measures in Catalina prevent Photos from opening a library on a volume that has been used for Time Machine backups. Apple has included warnings into the Photos User Guide about storing a library on a volume used for backups since Photos 3 on High Sierra. System Photo Library overview for Photos on Mac - Apple Support

WARNING: If a Photos library is located on an external drive, don’t use Time Machine to store a backup on that external drive. The permissions for your Photos library may conflict with those for the Time Machine backup.

To rescue the photos in your Photos Library copy the library to a locally mounted volume, formatted and prepared exactly as described here: Move your Photos library to save space on your Mac - Apple Support

The "Ignore Ownership on this Volume" is a very good indicator, if a volume can be used to store a Photos Library. It is not necessary to set this flag, if you are using the volume only from one user account on the same computer, but If you cannot set this flag, the volume is not compatible with Photos and you must not use the volume to store your Photos Library there.