Photos Unable to Open Library

Consider to update to Catalina version 10.15.2. It has many important bug fixes.Where is your Photos Library stored? On an external volume or in your Home folder on your system volume?

• If your Photos Library is on your system volume in your home folder, try to repair the permissions on your home folder as described here: Resolve issues caused by changing the permissions of items in your home folder - Apple Support
• If your Photos Library is on an external volume, check if it is compatible with Photos. Because of the im proved security features in Catalina, Photos may not be able to work with the library, if the volume is not compatible. Check the requirements here: Move your Photos library to save space on your Mac - Apple Support

Try this article https://support.apple.com/en-us/HT204967

Once you upgrade the Mac , did you used time machine to back up https://support.apple.com/en-in/HT201475

It is not necessary , you had changed the home permissions .

It's better to clean the hard drive and reinstall Mac OS https://support.apple.com/en-me/HT204904

Take suggestions from apple support https://support.apple.com/en-me/HT201232

You are still using Mac OS 10.15.1 update your Mac to 10.15.2 https://support.apple.com/en-us/HT201541

tygb, K12-Art already stated, that the repair did not work.

And I would never recommend a library repair anyway, before we know, where the library is stored; it can make matters worse, if we try to repair the library, if it is on an external volume, that is not compatible with Photos. We need to know, where the Photos Library is currently stored, before we can proceed with any fixes.

• if the the library could not be repaired, even in the Home folder, repairing the home folder permissions will help to be able to run a library repair.
• If the library is on an external volume, we have to check, if it compatible.

Not necessary repairing home permissions will always work , the photo application is corrupted , erasing the hard drive is far better than archive installation .