First, if by “several years”, you mean pre-Reloaded or early Reloaded, you’d probably be better off with a new account, as SM has changed a lot in a couple years.
With that out of the way, you were likely banned because admins found significant evidence of hacking / exploitative bug abuse on your account (big shocker, I know). If you believe that you were unjustly banned, check out this post to see what options you have for ban appeals: