Nothing. The interlock is only a requirement if you drive or own a car. If you don't then there is no problem.
This is just my opinion and not a comprehensive answer. You assume the risk because this answer may not apply to your situation depending on the facts.
You can sell the car. However make sure you fill out the proper paperwork with the court and the DMV stating that you no longer own or posses a car so you get credit for that time.