To access all your photos, update this Mac to the latest version of macOS - Running Monterey 12.6

Hello Scott_Fitz,

First, you'll want to back up your photo library to make sure all is safe and sound. You're able to do this using Time Machine, iCloud, or a third-party backup method: How to back up your Mac - Official Apple Support

Then complete the following steps to see if they help to resolve this issue:

"Create a new Photos library and see if your issues persist:

1. Quit Photos.
2. Press and hold the Option key while you open Photos.
3. In the dialog that appears, click Create New.
4. Give your new library a name, then click OK. Note whether Photos opens successfully with this new library.

To return to your main Photos library, quit Photos. Then open it again while holding the Option key, select your main library, and click Choose Library.

Alternatively, you can open Photos in another user account on your Mac and note whether Photos opens successfully.

If Photos opens with the new library, or in a different user account, it might mean that there's an issue with your library. Follow the steps to use the Photos library repair tool on your main Photos library."

The above steps and more can be found here: Get help with the Photos app on your Mac - Apple Support

Keep us posted.

Take care.

It is not an error, it is behaving as intended. You can enable the shared library on your iPhone, but do not automatically move your photos into the shared library, when you enable the shared library. The problem is, that the photos you add to your shared library are removed from your personal library, so you will not have duplicates across the shared library and your personal iCloud library. And then you cannot see the shared photos any longer at www.icloud.com or on a Mac with Monterey or older or on an iPad with iPadOS 15. Add only selected photos to the shared library, that you do not need in your personal iCloud Photos Library on devices with an older system. I am duplicating the photos I add to the shared library, so a copy will remain in my personal library, when I share them. I prefer to keep my personal iCloud Photos Library unchanged, when I share my best photos in the shared photos library, so I am sharing only duplicates.

I am not sure - there is not yet any documentation by Apple; without a shared iCloud Library a duplicate photo will not use twice the iCloud Photos storage, unless you add adjustments to one of the versions.

The error message could have been clearer. The Shared Library feature isn't scheduled to be supported on macOS until Ventura (expected to be released later this year, maybe ever later this month).

Scott_Fitz,

Thank you for that info. Deleting the shared library and the recreating it sounds like a good option to try. Keep us posted on how it goes.

Regards.

I have the same problem because my MacBook Pro 2015 can’t update Ventura.

Duplicating the photos is a smart solution. My question is: Will that double the size of the iCloud photo-library?