Imessage won't work

[bwhicher]

I have a iMac 2011, iPhone 4, iPad 3, and a mini.

I can not, no matter what I try, get my iPad 3 to send or receive messages. It tries to send then as progress bar gets to about 90% it stops and give an error not delivered.

All use the same iTunes account, all message account setups are the same.

The

 

[bwhicher]

Think I found problem.

I took backup from iPad 1 to setup this ipad3 and the iPad cellular dater number in contacts was old number and not the current iPad 3 number.
Nothing would send or receive, strange. Working now after I changed the number in contacts within iMessage.

Bob