Time Machine Backup Error with iCloud Drive Syncing on Sequoia 15.1

This isn’t about multiple accounts I have only one on my Mac, and this happened to me today after a full disk wipe and reinstalling macOS Sequoia. Looks like the iCloud upload progress is bugged. In Finder, clicking the “i” icon next to iCloud just shows the upload progress going up endlessly and never finishing. Didn’t have this issue before updating to macOS 15.2.

The workaround: disable iCloud sync completely, make a Time Machine backup and then turn iCloud sync back on. The files showed up again and the backup on external drive.

I had this same problem and there were no unsynched files on either account. I disabled iCloud Drive on both accounts and Time Machine immediately started backing up my iMac. I then enabled iCloud Drive on both accounts and further backups continued without a problem. I saw another thread on here that gave me the idea of disabling iCloud Drive.

if you have more than one user account, I have seen it reported that it might be the other account that has un synced files.

If it is sinking to iCloud Drive, you would see a little pie shaped icon, indicating the status next to iCloud Drive in the sidebar