I'm unable to register iMessage. Any suggestions?

[iMore Question]

I keep getting not registered with iMessage when trying to send an iMessage to a friend, yet when I send it from my iPhone or iPad it works fine, it just does not work on the Mac Air. Any suggestions? IT worked fine a few days ago

 

[zerog46]

Have you tried logging out then back in?

 

[ajl]

Try force quitting the Messages application, then reopening.

 

[Just_Me_D]

Did you get the problem fixed or do you still need assistance?