It depends on the reason you cannot access your account. There may be 3 different reasons:
1. Some times ago AGE requested a password change for security reasons, if you didn't do it, you have to do it now. You need to remember the email address bound to your old account to reset the password; logout form website then use this link https://www.aeriagames.com/user/pass_request
for a password change request, you'll get a mail that will allow you to do so.
2. If your account (as you said) is banned, you need to send a ban appeal and discuss with a GM if the ban can be cancelled. Use this link: http://www.aeriagames.com/contact/ban
You will still need your old email address bound to that account to change the password after the unban
3. Sometimes account can be wiped for inactivity (if no access happens in 6 or more months). In this case may not be possible this retrieve it, but it is still worth a try, sending a ticket to support: http://www.aeriagames.com/contact/support
It is easy to see if the account still exist and if it is banned or not, accessing your profile page.
This is my profile page: http://www.aeriagames.com/user/pask81
change "pask81" with your old username and see if you can access the page.
If you get the page, then you just need to change password; if you get "access denied" then your account is banned atm; if you get page not found it may mean that the account doesn't exist anymore.