Heater not staying on.

You’re not allowed to ask about a furnace this time of year! Check back in the fall.

Kidding aside it could be many things. Obstruction, limit switch, sail switch, 12v valve, orifice needs cleaning……and many other things. Very hard to troubleshoot without testing several key components. Are you sure it is not shutting off due to not calling for heat? (To warm)

It sounds like the high limit switch is shutting it down. Check your intake and exhaust for blockage from insect nests or some such thing. If there is an obstruction in the exhaust, for example, heat would build up and shut down the furnace. I once had a similar problem and found about a cup of bees and other flying critters in the combustion chamber. Check out the manual here.

Inadequate air flow in the RV ducting. Heat exchanger is over heating as said above. Could be an obstruction or just poorly installed to minimum specification. I tried to prop open my collapsed ducting in the floor for some improvement but still not enough. Solution was to add two more ducts through the cabinets and it works beautifully. Tons more heat too.

In addition to what was suggested above, out of LP gas, or valve is shut off.

I pulled the 4 wire plug on the heating unit and it was filthy with dirt and fuzz.I cleaned it and plugged it in and unplugged it a few times and now it works great.
Thanks for all your help.
Bless y'all.