This operation has been rate limited due to an earlier error:
Request failed with http status code 503
503 is a server-side error (“Service unavailable”) indicating that the iCloud servers are temporarily unable to handle requests from your devices / account.
This problem was widespread and affected many apps and users in early 2022. While Apple says they have fixed the problem, this still seems to happen randomly for some users.
The good news is that it usually resolves within a day. If you’d like to resolve the problem immediately, you can consider switching to Dropbox sync for now. You can sign-up for a free Dropbox account if you don’t already have one.