More details please.........
Model of Dutchmen?
Brand/Model of water heater?
Is water heater Full of water ---Cold inlet valve open, Bypass valve CLOSED?
Opened closest faucet HOTSIDE with water supply ON to allow water heater to FIll and bleed air from system
If gas model.....
Is propane valved in service?
Have you used any propane appliance so LP System is pressurized and get flow
(light off stove top burners on HIGH and let them burner for a minute to get fll pressure/flow established)
Water Heater......might need several attempts to get full propane flow to water heater
Turn switch ON...if you get a solid red light turn Off and then back ON