I have a 91 Beaver motorhome and cannot get any of the LP appliances to work. Generator is also LP and works just fine. Turned the vapor valve on and off number of times. Disconncted the regulator ...
I went thru this with our first one, a 1999. Seems they were very common back then, an electric solenoid near the propane tank, and a detector inside that controlled it and turned the propane off if it got a sniff.
seems that got "cost reduced" at some point. Newer models, including our Knight, have a detector, but it only makes noise, doesn't shut off the propane.