Cant send Photos shared album invitation

Hello, Milrinon! Thanks for reaching out to Apple Support Communities. 

After reviewing your post, it seems like you are running into some issues sharing your Photos. You’ve done some great troubleshooting, so thanks for taking those steps. We definitely understand that not being able to share as expected can be a concern and we'd love to help. Let’s continue our investigation by determining exactly when this happens. First, test for this behavior in safe mode: Start up your Mac in safe mode.

Next, see if this behavior persists in a second user account on your Mac. If you don't have one you can use, please follow these steps to make a test account that can be deleted later: Set up users, guests, and groups on Mac.

Please let us know if you have follow-up questions about this issue, or if the issue remains unresolved. Have a great day!

Thanks for getting back with us about this issue, Milrinon. Thanks for letting us know that your wife's Apple ID is working as expected. What happens if you make a second user account on your Mac but use your own Apple ID instead of your wife's ID? That will let us know a bit more about this issue so we can help to best resolve it.

Thanks and take care.

We appreciate you taking that step for us, Milrinon. Since this issue is persisting on every device you try and in all modes, it would be a good idea for you to have your account investigated further. We'd like to advise that you reach out to our Apple ID support team to look into this. Depending on your region, you may be able to reach them here: Get Support.

Thank you for participating in the Apple Support Communities and have a wonderful day.