When I hold down the option key and open photos, I don't get option to select or change libraries. Any tips?

Safe Boot from the HD, (holding Shift key down at startup), does the problem occur in Safe Mode?

Safe mode attempts to repair Disks & clears lots of caches, so if Safe Mode works try again in regular boot.

Hello,

Has Photos been completely quitted when you try and open Photos while holding the ⌥ (Option) key?

Press and hold down the option/ alt ⌥ key whilst opening Photos and the Library screen should show.