My iMessage works on my MBP and on my iPhone 5, but it's not working on my iPad 3. I can see messages, but when I type in a response the SEND button will not work. The messages are all from iOS users. I've turned iMessage off and on, airplane mode off and on, restarted my iPad. I checked my settings to match the settings on my MBP and my iPhone 5, but nothing is working. Does any one have a solution as to why the SEND button does not work?