Problem with iMessage

I am having a problem with activating iMessage on my wifi iPad 4. I previously was getting messages from my phone transfered to here, but all of a sudden it stopped working. I try to log in on iMessage and it just says that a error had occurred during activation. Every single time. I've logged out of my iTunes and iCloud and have shut off my iPad plenty of times. It won't just let me 'turn off' my iMessage either. I don't know what else to do..