Apple iMessage “An unknown error has occurred” cannot sign in on MacOS – Solved!

The Problem:

For a number of months I have had an issue with being able to sign into the Messages (iMessage) app on MacOS on my Macbook Pro. What happens is that I try and login, but the loading circle will rotate for 2-3 minutes and then “An unknown error has occurred” will be displayed.

It doesn’t matter if you disable Firewalls, disable anti virus, or boot the Mac into safe mode, this issue seems to persist without a solution.

I did mange to find some related solutions that kind of half worked, but none of them seemed to correct the issue on a permanent basis. For instance, this command ran in a Terminal window did seem to force a reboot and allow Message to login ONLY if you ran it whilst keeping the above error & Messages app open.

sudo -v ; killall -9 accountsd ; defaults delete MobileMeAccounts ; mkdir ~/Library/Accounts/Backup ; mv ~/Library/Accounts/*.sqlite* ~/Library/Accounts/Backup/ ; killall -9 accountsd ; sudo reboot

That line essentially deletes some iCloud info and then forces the computer into an immediate reboot. As stated, though, this command only seemed to work for a limited time and then if Messages stop syncing correctly or SMS messages failed to delete correctly between an iPhone and a Mac then the “An unknown error has occurred” would return when trying to log back in.

The Solution:

The solution to my problems was quite a simple one, it is literally a few steps…

  1. Ensure that MacOS is updated to the latest version. At time of writing iOS 16 introduced a ton of syncing issues with MacOS Big Sur. However, on October 24th 2022 MacOS Ventura was released with an update to Messages which seems to have fixed the iCloud messages syncing and SMS not deleting issues.
  2. Try and login to Messages, and get the same “An unknown error has occurred” error as before.
  3. Close Messages using Command + Q to ensure it is fully quit.
  4. Open FaceTime on MacOS. It should be logged in if you have activated FaceTime on your Mac in the past. But if not, go ahead and login.
    1. If you have the same error message trying to login to FaceTime. Leave the error on the screen and then open Terminal and paste in the code above. This will force a reboot of your Mac and then it should allow you to login to FaceTime without any issues.
  5. Once logged into FaceTime, keep it open and reopen the Messages app.
  6. Messages *should* open without an issues.

You can then go into Messages > Settings > iMessage and ensure your emails and phone numbers are the same as on your iPhone. You can also sign out of Messages and then try and sign in again to ensure the issues is fixed.

I have found that it takes messages about 24hrs to properly sync messages with iCloud. For me, I will have a sort half baked sync happen, but then once I leave my Macbook Pro M1 with the lid down over night, the next day the messages seemed to be fully synced.

I cannot stress enough how important it is to be on MacOS Ventura for iMessages to sync fully and for SMS messages to be correctly deleted between devices. Big Sur seems to have tons of issues due to the way that Apple reworked iMessages on its other devices with things like Editing messages and a Deleted Messages Folder.

Now I just need to work out how to get SMS messages to correctly delete on my Apple Watch (4+ years and counting). I have a Series 4 and an Ultra, but any SMS deleted from my iPhone or Mac will not delete on the watch. Also, if i delete an SMS on my watch it will not delete on the iPhone or the Mac. iMessages seem to delete fine, and SMS messages do change read state from Watch > Other Devices, but the “Delete Flag” never seems to sync between the Watch <> Other Devices 😡 It is so time consuming manually deleting SMS messages from the Watch interface and it drives me insane.

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