Welcome. You should have a 3" square black box with a red led behind the NoCold 1200. If the light is on it's stopping the 12V pwoer to the control board. IF not a 1200 and no recall box then the 12V fuse may be in your bathroom above the toilet. Probably 15+ 12V fuses...many for lights. Unfortunately the one for the refer may not be labeled so start testing all of them. These fuses are for the items that always have power to them unlike the front run box that only powers up when the key is on.
If you had a TT I'd say check the fuses next to the converter but a Navigator should have a charger/inverter with the fuse block behind a cabinet door somewhere...often next to the 120V circuit breaker panel.