Just checking if you have not done a copy and paste of your email address over to the email register box as sometimes this action creates an additional space to the end of your address thus making it invalid and cause the error.
Also to note is there might have been regional server issue (possible busy?) refusing registration but this normally goes away if you make another attempt at a later time.
If the aboves are not the case, could you share with us the make and model (and the version of operation system) of your device please?