Can't get iMessage to work on my iPad 2

iMessage used to work until iOS 6 came out and now it doesn't work on my ipad. I have tried several times to reset iMessage and reenter my apple id and tried all three addresses, .me, .icloud, and phone number but it fails. I have my ipad tethered to my iphone and it is passeing other data with other apps but iMessage will not work. Anyone have a clue how to fix this?