Hot water heater

I assume yours is a gas-electric HWH. If so, did you have it set to run on electric, or just on gas? We have had problems with past HWHs not being all that reliable on gas, but they worked ok on electric. Perhaps you need to set it on that instead. There should be a switch on the outside of the heater itself, plus one in the circuit panel. If it's a gas-only heater, then you may just have a blockage of the gas to it - spiderwebs are a common cause of that and can be cleaned out. They make special tools to do that (not expensive) which most RV supply places would have.