I agree with Les, that's its going to be one of the cut off valves. When we bought our Hi-Lo, we had the same problem. The previous owner had told us something about setting the water valves as part off winterizing it. In the spring I discovered that the valves were positioned on the hot water heater so that it got water, but no hot water could get to the trailer sink or shower. A twist of the knobs.. and we had hot water!
On our 2201, I accessed the valves for the hot water heater, from underneath the couch. Page 28 of this Hi-Lo manual shows the correct position for the valves.