Its a Glitch, It happened to me before.
I suggest you at least try now and see if it works, Cause the problem could be that when you finished registering, that probably the registration closed.
and can i ask you a question???
what type of email was it?? Shaw, Gmail, Hotmail??
cause if it was any other email
I suggest you try using Gmail, Cause for me, Gmail seems to be working the best with a lot of games i play
and my mom had a similar problem, she tried to send me something and it didn't send to me.
She mentioned that her email expired??
Could it be that your friends email expired??
If so, try making a new email, cause something could be wrong with your friends email, that could be a reason why it doesn't like it, cause sometimes only one email works the best..
for example, as i said at the very top, Gmail seems to be working the best on this game for me
So probably try making a new email and see if it works
Or try using Gmail