quick tell me what brand heater you have. I had the same problem with my suburban and I had my friend the RV tech look at it and it was only a wire that was not making a contact. what he did was ( if yours is a suburban) took the black cover off the heater and inside the there is two connector or circuits. the one on the right is the one you need to work on. turn on the switch in the TT for the heater to come on and then wiggle the lower connector. if it doesn't fire then wiggle the upper connector. if that doesn't get the propane to light then you may need a gas valve. yes the gas valve is very expensive. Any way that is what he did and the heater works great. and he did it for no charge. he just laughed at me. told me I should have called him months ago to get it working for me. we went to Yuma with it not working. it worked only on electric, but it was hot enough for us. good luck, I hope you are as lucky as I was.
