water heater not heating water

Hi folks,

Upon opening the TM for the season, the waterheater does not heat the water. The power supply is switched "on" inside the water heater storage compartment. The undersink switch is "on" and red light on (above the words "reset". Is there a fuse related to the water heater? When we opened the TM, the red light on front of sink was on and the fresh water system was not yet filled with water. Do you think we have damaged the water heater? It worked fine when we closed up last. Any trouble shooting ideas would be greatly appreciated.