My MacBook Air won't stay synced with iCloud
I have a client with a MacBook Air (running Sequoia current release). For some bizarre reason, the Mac can connect with their iCloud, but will not "stay" synced.
On two different occasions, I signed the computer out of iCloud ("not" saving contacts on the Mac, since there was some garbage in some of the contacts)), then re-signed into the client's iCloud (where the garbage was removed from the contacts before the signout/signin). The new calendar / contact information came down as "hoped", and all looked good. 15 minutes later, the syncing appeared to stop, because calendar entries and contact changes made on the Mac weren't making it to iCloud, and visa-versa. However, syncing with the client's iPhone (and the same iCloud account) appeared to work great.
Both the Mac and iCloud storage have plenty of space, the Mac is set to the correct time (and timezone), and other network activity on the Mac works great.
The temporary workaround is to put all contacts and calendars in a non-Apple account, but the client prefers to stay with iCloud if possible due to other Apple devices in that account.
This has been a problem for months, so any help would be appreciated. Thanks.
[Re-Titled by Moderator]
MacBook Air (M3, 2024)