How to set up iMessage on your MacSource: Joseph Keller / iMore

Apple rightfully has a reputation of having its products "just work." And 99% of the time, that adage holds true. Until it doesn't. When things do go wrong, Apple's error messages are cryptic, at times offering no obvious clue as to how to remedy them. One such error is the "Authentication Error" message when trying to log into iMessage and FaceTime on your Mac, even if you've successfully logged into iCloud.

The problem

For a non-obvious reason, my previously properly running Mac could no longer log into iMessage or FaceTime despite being successfully logged into iCloud. Notes synced, Documents synced, Photos was working, etc.

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Trying to log into iMessage triggers my two-factor authentication mechanism as expected. But when prompted for my iCloud username and password, and after a long timeout period, I simply get an "Authentication Error."

The potential fix

The fix involves getting Apple's servers to re-initialize your Mac hardware to be allowed to access your iCloud services.

Log out of iCloud on your Mac

  1. Open System Preferences.
  2. Click Apple ID.

    Log out of iCloud on Mac, showing how to open System Preferences, then click Apple IDSource: iMore

  3. Click Overview.
  4. Click Sign Out…

    Log out of iCloud on Mac, showing how to click Overview, then click Sign Out...Source: iMore

  5. Follow the instructions to keep or delete iCloud data like calendars, reminders, and photos from your Mac.

    Log out of iCloud on Mac, showing how click Keep a CopySource: iMore

  6. Restart your Mac.

Log into your iCloud.com web account

  1. Navigate to iCloud.com in Safari.
  2. Log in with your iCloud credentials.

    Log into iCloud.com, showing how to navigate to iCloud.com, then log in with iCloud credentialsSource: iMore

  3. Click Account Settings.
  4. Click your problematic Mac under My Devices.

    Log into iCloud.com, showing how to click Account Settings, then click on your Mac that's having issuesSource: iMore

  5. Click the X next to the Mac.
  6. Click Remove.

    Log into iCloud.com, showing how to click the X next to the Mac you want to remove, then click RemoveSource: iMore

  7. Click Done.

    Log into iCloud.com, showing how to click DoneSource: iMore

Sign back into iCloud on your Mac

  1. Open System Preferences.
  2. Click Sign In.

    Sign in to iCloud on Mac, showing how to open System Preference, then click Sign InSource: iMore

  3. Sign in with your iCloud credentials.
  4. Enter your Mac sign-in credentials.

    Sign in to iCloud on Mac, showing how to sign in with your iCloud credentialsSource: iMore

  5. Click OK.

    Sign in to iCloud on Mac, showing how to click OKSource: iMore

Once you're signed back into iCloud on your Mac, you should be signed back into Messages and FaceTime automatically.

Final comments

This is but one solution (of the myriad of suggestions found online) that worked for me. Let us know in the comments if this fix helped you too!

macOS Big Sur

Main

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