Unable to sync messages or reminders via iCloud after updating to macOS 26.0 Tahoe

rackner wrote:

I updated to macOS 26.0 Tahoe this morning and I am now unable to sync messages or reminders via iCloud;

Within my Apple settings I see the following error:

https://discussions.apple.com/content/attachment/bb676613-100e-4508-b55c-b46782f511b5

https://discussions.apple.com/content/attachment/45964a24-6096-4f70-bc38-828906f4ad74

When I try to 'Resume Data Sync', I input my password and then it perpetually loads without actually updating.

Similarly, within the Messages app, it tells me 'an unknown error occurred':

https://discussions.apple.com/content/attachment/bcec0aae-9fec-4f5d-9ecc-8e9b1896ea63

I have tried logging out and back into iCloud along with restarting my computer but the issue persists. Can anyone advise?

[Edited by Moderator]

I see no issue on the servers related to iCloud an sync services.

ref: Apple - Support - System Status

you can try again signing out and back in(?)

Check your >System Settings>iCloud and very the toggle settings, you can turn off and back on in an effort to elicit some change

Check your Apple ID device list to see where you're signed in

Check your Apple Account device list to find where you’re signed in - Apple Support

Sign out of your Apple ID/Account /iCloud on the Mac and back in again and compare your results

Sign in to or out of your Apple Account on Mac - Apple Support