Well, it look like you nor confirm email. Because the forum don't need to confirm email, however it requirement for playing game that reason you not valid. You will need make sure all things
1) You checked your spam folder? If you didn't, check that folder
2) Is your email provider a bit well known like Gmail, Hotmail or etc? Try probably making a new account with providers named as Gmail.
Or in some cases, maybe you need to copy and paste password into screen (as some error when you type in game). It also can solved by changing password too :Grin: Hope it can help you