No power from shore or generator, ok on inverter, need help

Keep a close eye on you 12VDC levels until you can get a bigger convertor/charger. 20 amps is very light for a Class A. My gas coach has an 60 amp unit to give you an idea of what might be needed. 12VDC is the life power of a coach. Lose it and no HVAC, fridge, water pump, jacks, slides and such. If your coach is configured to supply alternator DC power to the house you could start the engine to recharge if the charger has trouble keeping up.