After upgrading to iOS 7, I noticed that my iMessages were not coming through to both my phone and Mac like it used to. If I'm on my Mac, the messages will only be sent to my Mac, and they do not update on my phone. It's frustrating. I want my messages on both devices to be up to date. I have a MacBrook Air 13.5" inch and it will ONLY allow me to set up my iMessenger with my Apple ID. I went into my iPhone to make sure my Apple ID and phone number was enabled. It is. EDIT: Fixed my problem. All I needed to do was restart my iPhone.