Turned on the furnace the other day and nothing but cold air. Checked the changeover indicator and it was red but second bottle was still full. We have had nothing but intermittant problems with it since we bought the trailer. Enough is enough. Went to Camping World and bought a replacement valve and then the fun began. Of course the valve is a different brand (wouldn't wish this experience on anyone again) and the pigtail connection was different than the original, so bought a new pigtail. After 2 hours of hunting through Home Depot and Lowes an employee worked up a fitting for me that would adapt the 2nd tank line to the new valve. A little yellow paste and leak test later, with a slight shift in mounting position, and we were finally working again. It's done, but not one of my more favorable replacement projects.
We had the same problem one time on our new Big Sky. Found that the tank can block the flow when it senses something wrong. We unscrewed the line from the tank and tapped on the tank a couple times and that cleared it. It's worked properly ever since. The temperature at the time was below freezing. We asked a repair shop about this. Their verdict was that the safety in the tank sensed a piece of ice and would not permit gas flow until it was cleared.