Yeah, they only provide support if you have an active contract. Not sure what you mean by back-pay. My experience is that you just need to buy a new contract which would be good for a year.
I don't think there is any way to "reset" it without their help. Actually I don't know if they even have a way to reset it or if you just need to write a new CF. One thing -- did you change both passwords? There is a password for the web gui and also one when using secure shell or console to log in.
Since you had a contract, did you ever upgrade when they released a new version? If you still have a copy you could just write a new CF and start over with everything factory reset.