Your converter is suppose to charge your coach battery when connected to shore power. If the fuse/
circuit breaker which sits near the coach battery is blown then that would prevent the converter from charging the battery. If the fuse/circuit breaker is OK then you should be reading 13.6 volts at the battery when the rig is plugged into shore power - if not then the fuses on the converter need to be checked - if those are OK then your converter may need replacing.
If the converter is working and your batteries are still low - then have the batteries checked out at your local auto parts/tire outlet - may need new battery.
Also - your rig may have a battery disconnect switch - make sure you haven't accidentally triggered that since it will take the batteries off line preventing them from charging.
Kevin