I'd say you probably have some frozen water lines. You probably have low point drains under the trailer on the off-door-side. There is water in the drain tube, below the coroplast, but above the drain valve. That water freezes and the ice can wick its way into the tee, blocking water flow.
Try using a hair dryer on the hot water low point drain to see if that frees up the blockage.
Keeping the water running at 5 (F) usually takes some extra steps. You'll find a lot of helpful information in our owner-written
Water Systems Winter Usage Guide.