We were on our first trip of the year last weekend and the water heater stopped working. It would start up like it was going to heat the water but would shut down after about 45 seconds. We found the following video that shows where the reset button is. Evidently, it is a safety feature that engages when it senses the water temp is too high. Pressed the little white button and turned the temperature dial down and voila, hot water.
https://www.youtube.com/watch?v=eE89B4zQoKc
Mike