imessage suddenly stopped working on imac

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Messages – Can’t log in

Hi,

Do you have an iPhone linked to this Apple ID for iMessages ?

Does this still work ?

If so the issue is related the the iMessages Servers and the Mac's use of the Apple ID (the servers can block devices based on unique info that is part of the Auth Token).

In APplications/Utilities open the Keychain Access app

In here select Login at th top left, Passwords lower left and then find "IDS: yourAppleID-auth Token" in the right hand pane.

Delete this and restart Messages.

Is the Auth Token recreated ?

Can you login (And Send iMessages) ?

If you cannot you will have to contact Apple Support and explain you have an Apple ID issue with the iMessages Servers and can they have a look at it.

Most likely you will need to ask to speak to a Level 2 person to do this (Level 1's are very script led (software and hardware issues) and looking for AppleCare or payment but ID issues are free to fix).

10:20 pm Wednesday; April 22, 2015

Try booting into the Safe Mode using your normal account to see if Messages will work there. Disconnect all peripherals except those needed for the test. Shut down the computer and then power it back up after waiting 10 seconds. Immediately after hearing the startup chime, hold down the shift key and continue to hold it until the gray Apple icon and a progress bar appear and again when you log in. The boot up is significantly slower than normal. This will reset some caches, forces a directory check, and disables all startup and login items, among other things. When you reboot normally, the initial reboot may be slower than normal. If the system operates normally, there may be 3rd party applications which are causing a problem. Try deleting/disabling the third party applications after a restart by using the application un-installer. For each disable/delete, you will need to restart if you don’t do them all at once.

Safe Mode - Mavericks also Yosemite

Safe Mode - About

Try setting up another admin user account to see if the same problem continues. If Back-to-My Mac is selected in System Preferences, the Guest account will not work. The intent is to see if it is specific to one account or a system wide problem. This account can be deleted later.

Hi,

Do as Eric says (create a new Mac User and test there - use the same Apple ID to set up iMessages).

If it works here then it will be something about the settings (.plists or Keychain) in your regular Mac User account.

If it does not work then it will be something at the Server end and only a call to Apple Support will solve it.

9:38 pm Thursday; April 23, 2015