The following error can happen for these reasons.
1 - Your account is deactivated; you can activate it from the account panel on the website, which sends you an activation email.
2 - Your account is blocked. If it is temporary, the anti-bot detected something malicious on your PC, and that block lasts 30 minutes. Keep in mind that if you do not fix the problem and try again, it blocks you for another 30 minutes. The only known false positive is Team Speak’s OverWolf program — do not have it installed.
3 - It may be permanently blocked, and you will have to contact the administration to find out why.