I just looked up the 2008 Navion Owners Manual. It is here if you need it.
There is a propane water heater switch on the panel with the level test button and the water pump button. I don't recall if this switch lights up but it does have a little round warning light if the pilot light does not light.
There is an independent switch that says Water Heater 100 volt. This switch should light when turned on. Make sure there is water in the Hot Water tank before turning this on.
I am not sure of the third switch you mention but the Navions do have a switch at the control panel area that turns on the propane supply to the coach. You will not get any propane flowing if this switch is off. There is also a matching switch outside in the propane bay itself.
If the propane supply switch has been off a long time it will take a while to get propane to the appliances, water heater, fridge, generator. We usually turned on the propane supply then turned on one of the stove burners and kept trying to light it until it ignites. Once it ignites you can turn it off and try to light any of the other propane appliances and they should light more quickly.
Norm & Ellen Proud to be one of the HOOTS
2015 Newmar DutchStar 4369
If I knew retirement was so much fun, I would have done it in my twenties!