Hello XXXXXXXXXX, my name is Jeff.
It sounds like you may have a bad board or gas valve. The board tells the gas valve to open and then the ignitor to light once everything is going, if it is trying to light, then this process is completing but the board may not be opening the gas valve. The only to be sure is to have the board tested with a board tester to make sure that it is working correctly. Most of the furnaces are pretty easy to remove and you should be able just to take the entire furnace in to a repair facility without having to drag the camper down there. That way they can bench test the unit and tell you exactly what is going on with it.
I hope this helps, to me it does sound like the board. I would definitely have it checked before spending 100 to 150 on a board.
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Regards,
Jeff Myers
RV Mechanic
Owner of an RV Repair Facility for 9 years. 12VDC and 120VAC, ALL Appliances, Any and ALL problems!