Seriously though, most interior lights, in most RV's always run off the batteries even when you are plugged into shore power. Therefore your battery is not being charged, one the circuit breaker is tripped as some have suggested or 2 your converter is unserviceable, (broken). Also some converters plug into an AC outlet, check that it's plugged in securely. Or the DC output from the converter is not getting to the battery. There could be other issues as well!