I've got this notification, and when I press 'resume sync' it's asking for the local password of an iMac I had around 2010. I've no idea what that password is, and I removed the device from my Apple account a long time ago.
How can I clear this notification? Even when I dismiss it it seems to open the system settings by itself.
MacBook Pro 13″, macOS 15.7
I haven't ever gotten that, but I wonder if you have encrypted files or folders. Have you looked at "logging items" in System Settings?
To narrow things down, try a re-start in Safe Mode. This bypasses certain potentially disruptive processes, and it often helps. Safe Mode is different for different computers, so see this:
Start up your Mac in safe mode - Apple Support
Also, try making a new user and see if the same problem recurs with it.
"Some iCloud data isn't syncing"
