No hot water

lesstatt

we have a 2010 autotrail Mohawk motorhome and we drained the water away for the winter a few weeks ago, we have come to use it today and filled up with water however we appear to have no hot water, the truma water heater isn't filling up at all, the pump
runs fine and we have cold but no hot. The clear plastic pipe that goes in to the unit has no water in it. I have pulled it off and sucked but no joy as such. Can anyone offer any advice at all ?.