Well I don't know the exact details of why you can not get it, But make sure you are checking every folder (Including Junk/Spam) Of your E-mail, The Title of the message will be "Action Required to Activate Membership for MPGH - MultiPlayer Game Hacking". If you can find this, Simply follow the directions given.
If this does not work you might want to have this E-mailed to another address, You can do so by changing your Address here;
If none of these steps work your last choice would be to contact the Head Administrator (Head Judge) ; Dave84311
MPGH - MultiPlayer Game Hacking - Show Groups
Please understand that Administrators get inundated with requests and messages all the time, Be polite and patient.