[NewellCrazy]

There are several possible issues

Here is the sequence of events that SHOULD happen

Thermostat calls for heat, Blower turns on and air begins to move,
As the air moves a SAIL SWITCH inside the furnace senses air flow and closes
Burner lights and air gets warm... As rig heats up Thermostat signals "Hot enough" and burner shuts down
Fan may continue to run for a few seconds or may shut down promptly

Possible issues are MOSTLY with the air flow.. If something has "nested" in an air duct, air flow will be reduced. If you have a throw rug or other object blocking more than one air vent, air flow may be reduced, if there is "Crud" build up in the ducts, air flow may be reduced, if a duct has collapsed,, Air flow may be reduced

If the batteries are low, the blower can not come up to speed and air flow is reduced

if the blower is worn out.. Likewise

If air flow is reduced the sail switch won't sail closed and thus the burner won't light

To test.. You need to check the state of the sail switch.. I am afraid I can not help much there as I've never actually looked at the control board for my heater.

Next.. We have burner issues.. There is a spider that loves to next in gas jets, clogging the jet and preventing ignition. I've cleaned quite a few spider nests out of assorted gas jets.. NOT, so for, on the RV, but on other stuff.

Next we have the ignition point (Assuming it is and ESI system) you should HEAR it sparking, and if you can observe the points you should SEE It sparking. I have seen points way, way, way out of adjustment (Reset them and years later that furnace was still functioning properly)

Next we have the thermocouple (Flame sensor) if it's bad it signals the control board "NO FLAME, Safety shut down"

Now we have the control board and last the gas solenoid

And that is just about the list for the symptom (no heat) you have

Most of 'em are easy to fix, and with the exception of the control board and solenoid, not too expensive