unknown error occurring with iMessage on Mac

Thanks for the info; that's really frustrating (and I know because I spent 10 days trying to fix this problem myself before I finally cracked it). I tried a bunch of the steps you posted above to no avail.

First I would run a backup of the new computer. Then I would try signing out of iCloud on the new Mac, opening Terminal and running the following command:

defaults delete MobileMeAccounts

I got that command from here:

https://apple.stackexchange.com/questions/340155/account-is-already-signed-in-to-icloud-in-mojave-but-its-not?newreg=804cdc6d23fb475dbbf208c736a5e109

That's the step that fixed everything for me. Although, in my case, my old Mac was also having problems with iCloud that started after I tried signing out of iCloud everywhere to fix the Messages problems on the new Mac.

So I ran the Terminal command on the old Mac which fixed the iCloud problems on that computer, erased the new Mac and reintalled MacOS, used Migration Assistant to copy all my data to the new Mac, and after that Messages worked on the new Mac. So your case might be a little different. I also used Onyx by Titanium Software on the old Mac to just clear out the System Cache and run some routine maintenance before running Migration Assistant.

How long have you been using the new Mac? How feasible would it be to do a erase and reinstall? I know it would suck to do that if you've already tried similar steps, but it might be necessary—I went through 5 erase-and-reinstalls before I finally fixed everything.

Hi Jacob, Thank you for the quick reply and info. I just tried that and it didn't work. Now I'm going to sacrifice a chicken or something, maybe this iMac.

It is a 2019 but new to me. I just started setting it up today so a wipe and clean install is not a big deal.

I'm going to try downgrading to Bigsur and then see if messages works there, if not I'll let you know.

I appreciate your help and will get back here tomorrow to let you know how it goes. I'll also file the fix you gave me away for future reference.

Here's an update: Downgraded to BigSur and briefly saw I was logged into Messages (about 10 sec) then logged me out.

Created a new Apple ID, same thing.

Contacted previous owner, they'd had the logic board replaced. Turns out the serial number reported in "about this Mac" and the serial number on the iMac foot are different. going to contact them and see who did the replacement and see about settling the serial number issue, from what I've read today on the net, that difference can be my issue.

I'll post back next week with findings. Thank you again Jacob.

Latest update: Have restarted, shut down and started up, downgraded to Mojave, BigSur, now back on Monterey 12.4. Have made second user account, have changed iCloud password, run terminal command to delete mobile me accounts, have deleted some pref files like Madrid and apsd.plist and messages and ichat user library pref files, etc. Have been on 2 calls with apple tech support, no one has fixed this and messages and FaceTime are still not usable on this iMac. It shows up in My devices in the iCloud list, all other iCloud type things work. A sledgehammer is about the only thing I haven't tried. I'm open for other suggestions before I do that but am getting closer daily to using the trusty sledge.

Jordan, you have no idea how much I appreciate you right now. This actually worked!! I have tried almost everything and got as close to doing a factory reset. Thank you! I am sending you some positive energy your way – hope you have a wonderful day! @jordanwinston

Hi @Cnaz

I hope I am able to help. Looks like you're taking the right steps, except––after you create the new account, (don't create a temp account) you will go into the new account you've just created, sign in to your iMessage, and iCloud just like you did, like you mentioned it work after you're logged in, do not log out of the iMessage. Now switch over to the account that you're actually using that is giving you the unknown error, try signing in to the iMessage and iCloud –– this is when it worked for me. The only thing is that I have not deleted the new account I created because I'm afraid it will stop working on the account I am using. Let me know if it works!

For anyone else who comes across this later, I experienced this problem this morning. Very strange in that it just came out of the blue after no issues for so long. I tried a lot of things as well but ended up just signing out of iCloud entirely, rebooting and then signed back into iCloud (by this, I mean machine-wide in the Internet Accounts section of settings...doing this in Messenger alone got me nowhere). It fixed the problem.

Im getting the SAME error and NOTHING seems to work. What is going on?

I am also getting the same error after installing 12.1 ... has anyone actually managed to solve this yet?

... and I was just about to try this and I was able to log in and my messages suddenly starting working :-P Keeping for future reference though. Thank you @jordanwinston!

You're a legend thank you

My advice is don't even try anything else, this is the only thing that will work.

exactly jcjycht -- i tried so many other things -- that's the only thing that worked.

@jordanwinston! You are legend.

This worked. Many thanks, friend!!

Hello! I got an MBP with BigSur 11.6.2.

I had this issue today for the first time ever.

i restarted the Mac and everything turned on again. conversations are not synced but it's okay