Your converter/charger could be right behind your house fuse panel. If you have a dashboard 'boost' switch that connects the house and chassis batteries together while the button is held down, you might start the engine, then use the boost switch to supply power to the house battery to pull in the slide, if that's what you want to do.
You should put the house battery on a charger, then take readings on all batteries alone, then while plugged in to shore power to see if your converter/charger is working. (There should be a voltage increase under charge) If no change, check on the sides of the converter/charger for a circuit breaker that may have been tripped.
Bob & Donna
'98 Gulf Stream Sun Voyager DP being pushed by a '00 Beetle TDI