Since the converter provides 12v power rather than 120vac, that's not your problem. However, it is possibly part of, or behind, the 120v load center if that also contains the fuse panel. If it does not, follow the big cable from the battery positive post - it goes to the converter.
If you have no 120vac power, odds are a wire is broken in the shore cable. Most often where the plug is attached - it gets a lot of wear & tear. If that's not it, check the other end where it connects to the circuit breakers (load center).