It does sound like you have gone over the level limit, and if so, only the developers can help you out now.
There's a small chance that the problem has been fixed in a recent update (i.e. between the v2.4 that you're using and the current v2.5B), so try to get the most recent version running if you can.This guide
might help you clear your cache & cookies, if what you've already tried hasn't worked (it says battledawn on it, but it should work for supermechs too).
That's all I can do to help, now you're just stuck waiting for a modmin or one of the game developers to show up.