You must sign in with your Apple Account (formerly Apple ID) to use iMessage on your Mac or sync your iPhone documents to it. It’s a simple process, but in some cases, you may see random errors that prevent you from signing in. Go through these quick tips if you see “An unknown error has occurred,” “Authentication error,” or another similar message when you sign in to the macOS Messages app with your Apple Account.
Make sure you enter the correct information
If you type your Apple Account email address and password incorrectly, the app should display the appropriate message. But in some cases, it will just throw the usual “An unknown error occurred” text in red on the screen. So, double check that you are entering the correct information. If you ever forget your Apple Account password, reset it immediately from iOS Settings or macOS System Settings.
Try again after force quitting the app or restarting your Mac
It is also possible that even though you are doing everything correctly, the application keeps showing an error message because it is still connected to the previous issue. To fix this, force quit the Messages app by clicking the Apple icon in the upper left corner and choosing Force Quit. Then, reopen the app and try to sign in again.
If force quitting it the first time didn’t help, force quit it again, then restart your Mac. Then, open Messages and try to sign in. It should pass successfully.
Check the status of the Apple system and try again after a while
Visit Apple’s system status page and make sure things like it Apple Account, iCloud Account & Sign Inagain iMessage are available. If it stops, wait and try again after a while.
Update to the latest version of macOS
If your Mac is on an older version of macOS or running a beta version of macOS, upgrade to the latest build available on your computer.
Delete system files related to messages
If you still see “An unknown error has occurred” or another similar message, follow these steps to delete related system files and restart. Since you are already logged out, deleting them should not cause any concern. After restarting, macOS will recreate these necessary files.
- Go to your Mac’s hidden Library folder by opening it Finderholding the An option key, and click Go away > The library from the top menu bar.
- Find and open the file Messages folder. Then, select all the files and folders here and move them to the trash. You can also move them to another folder for safe keeping.
- Important: Restart your Mac.
- Open the Messages app and try signing in again. It should work.
Sign out of your Apple account and sign in again
If you continue to experience sign-in problems even after following the tips above, consider signing out of your Apple Account in System Settings. Then, restart your Mac and try signing in to Messages again.
If all else fails…
Finally, if nothing works for you, I recommend you wait a few hours or maybe a day and try again. If you’ve done that and the problem persists, try this as a last resort. I listed the simplest ones above.
If you’re successful, that means there’s a problem with your specific user account or macOS installation. Again try all the solutions above, especially the one where we talk about deleting all the Messages files and starting over.
If the problem persists, consider these two options:
One or a combination of the tips above should have solved the iMessage sign-in problem on your Mac. Let us know which one worked for you.
Also, check out: How to sync all iPhone messages on Mac