Photos Error when trying to send to my Shared Album

Hey there zoe_aleah,

We'd like to confirm more details to better understand what's happening, along with ruling out some possible causes:

1. When did this start to first occur with your shared album?
2. What device did you use to take the photos originally?
3. Are you able to add photos taken with other devices to the same shared album?
4. What occurs if you try adding the same photo to the shared album using the iCloud website?
5. Sometimes unexpected behavior can be resolved with a restart. Check out the section 'Restart' here: Log out, sleep, wake, restart, or shut down your Mac
6. Since you have a compatible Mac model, the latest version is macOS 13.1. You can verify this by clicking on the Apple logo at the top left corner of the screen, then on ‘About This Mac’. In case you needed it, this link shows how to first back up, then Update macOS on Mac.

Cheers!