I do own a 31 foot 5th wheel and it does take a few attemps to get the furnace
due to air in the line.
What happens when you turn on the thermostate to heat and then turn up to above indoor temp?
You should hear the furnace
fan turn on followed by the electric spark ignitor..it will click about a 12 times then rest...and do it again...3 times
If it doesn't light
..repeat...if still doesn't light
, make sure you have enough electricity to open gas valve.
Now after hearing it run you should know where it is and check where gas lines run to it, inside or outside and make sure if there is a gas valve that it is turned on.
works of 12 volts but needs good battery
or shore power to run. It takes alot of power to open the gas valve with the fan running also.
If hooked up to shore power make sure your switch is turned on for the converter...if not you may be running just off your batteries and may not have enough power to open gas valve.
If none of the about works...find outside of furnace hatch and there will be a reset button on the motor to make the fan work.
All these controls work one after another for safety.
If still doesn't work bring it in to a repairman.