cannot calloborate you’ll need to use Numbers on iCloud.com or Numbers on a newer Mac.

This is happening to me as well, except I cannot update. My Mac is 2015 and is no longer eligible for new iOS updates, so I won't be able to fix the collaborating issue. Bummer. It's stuck at Monterey.

Hey there HornSwaggled,

Thanks for reaching out to Apple Support Communities. We're happy to provide some assistance.

The actions in this article can help with the issue you're describing:

Collaborate on documents in Pages, Numbers, and Keynote on iPhone, iPad, and Mac - Apple Support

"If collaboration isn't available

If you use Pages, Numbers, or Keynote and collaboration isn't available, you might need to update your apps on your iPhone, iPad, or Mac. Turn on automatic updates so that your apps always stay up to date. If your device is too old to update your apps, you can still collaborate online at iCloud.com using a Mac or PC. 

If you want to send a copy of the document, you can send it without collaborating. Click or tap the Share button, choose Send Copy from the pop-up menu, then choose how you want to send the document."

That article also provides additional information on how to collaborate using your Mac.

Keep us posted.

Have a great day!

Looks like I have the same problem’s

Same issue on 13.5.1 this morning. Walked out on Friday and everything was fine. Today this happens, even after a restart.

Turns out my system had a pending, minor, Numbers update which had not yet triggered. This is a truly unacceptable way for this to function: If apple expects people to use their products they need to 'just work' - instead 'just not work' - it is a subtle on-word difference, but it means the world to your end-users.

Check your updates, if any one of your shared users has the update, even a minor one, you'll apparently need to make sure that all users are on the same exact revision (i.e. 13.2, not 13.1.9, or 13.2.1, or any other tiny little discrepancy.)