It took me a while to figure out the hot water system, once you get the "basement" access panel off you will see a maze of color coded pex pipe. Next to the hot water tank there is a line that bypasses the hot water tank, you have to close this ball valve and open the red line ball valve. If your trailer has been winterized opening this valve may introduce anti freeze into the system again (a small amount) so you may have to re-flush the system. While you are in there it may be a good idea to check a heat sensor that is taped to the side of the water tank, it sometimes comes off, so make sure it is still taped to the side of the tank.
When I first took mine camping we went without hot water for almost a week before I figured the system out. If you are heating with LP you can go through a tank in a couple of days, I only use LP when in high demand, and keep it hot with electric switch on main control panel.
I still feel like it is running a NASA rocket sometimes to keep everything running right.