Photos Library won't open

and NO "ignore ownership on this drive" checkbox in the external drive info window.

If the "Ignore ownership" flag is missing for the external drive, you are using a drive that is not compatible with Photos for Mac.

Typically, this flag will be missing, if the file system format is not MacOS Extended (Journaled) or APFS, or if the drive has been used for Time Machine backups or other backup software is installed, or the volume is a NAS or accessed over the Network in any way. Then you simply cannot use the external volume for a Photos Library.

Move your Photos Library to a volume, that has been prepared as described here: Move your Photos library to save space on your Mac - Apple Support

Hi there pdaviesoz,

Thank you for choosing Apple Support Communities!

It sounds as though you’re seeing that a Photos Library stored on an external hard drive is not able to open. You’re in the right place, we’d be glad to assist in seeking a solution.

Below is a resource that can help:

Get help with the Photos app on your Mac

We’d advise trying the steps in the “If you're having other issues with Photos” section.

If Photos can open successfully with a new library, try opening your Photos Library in another user account on your Mac:

How to test an issue in another user account on your Mac

If the Photos Library can open successfully in a new user, try using these steps on your Main Photos Library:

How to use the Photos library repair tool

We hope this helps,

Cheers!