On the next screen, use the slider to Power OFF your device. Go to Settings > General > scroll down and tap on Shut Down. Restarting iPhone can often fix problems by terminating stuck processes, which might be preventing you from signing into iMessage. If none of these methods work, you can either Create a New Apple ID or contact Apple Support and find out if your Apple ID has been blocked or placed on special status. In most cases, this problem can be fixed by using one of the methods as provided below. In a typical case, you will see an error message reading Unable to contact iMessage server or An Error occurred during activation.
