Photos library won't open

MickLead wrote:

I am also able to view the photos on my iCloud account.

If you can view your photos on your iCloud webpage at www.icloud.com , the fastest way to recover your Photos Library would be to let the Photos.app download your photos from iCloud to a new, empty library.

The Time Machine backup may be incomplete, if you have been using iCloud Photos and syncing the restored library again with iCloud would take longer than just downloading to a new, empty library.

You may want to try the following:

• Quit Photos, if it is running and launch it gain while holding down the ⌥ key until the library chooser dialog appears.
• Select to create a new library. Create it in your Pictures folder, with a new name, so you can easily recognize the new library.
• When Photos opens with the new, empty library open the Photos > Settings with the key combination ⌘, and click "Use as System Photos Library".
• Then switch to the iCloud pane of the Settings and enable iCloud Photos for the new library.
• Now wait for your photos and videos to come back from iCloud.

All your albums, folders, photos and videos and the metadata should come back from iCloud, if they are still in iCloud. The only thing missing will be the projects - your slideshows and books and other third party print projects. For the projects you will need to start over from your backup.

The copy of the Photos Library would - most likely - be in the Pictures Folder of the back up. It will be called Photos Library.photoslibrary

Obvious question: do you have a back up?

Open Other should bring you to a menu for other libraries. Have you more than one?

Where is the faulty library stored?

Where is your new Photos Library, Mike? Is it on the internal disk in your Pictures folder or somewhere else?