First, are you getting any power when on 12 volts?
If there is a dummy light on the converter, check to see if its lit to see if you have any power to the camper when on batteries (The area below my fridge where the converter and fuses are has a light that will always be lit when powered by batteries or AC).
Assuming that is lit while on batteries and still no lights, I would check fuses and then your light fixtures (with a multimeter) for current, and then the bulbs. Unlikely that all of the bulbs are bad but who knows.
Your water pump will work on battery.
DW, 3 Kids and our Goldens
2012 Shamrock 233S
2008 Toyota Sequoia 5.7L 4WD