I'm glad to hear ALL valves were open! If the valves were still in "winterize" mode, you'd be trying to heat water that wasn't there. An empty water heater tank. That will burn out an electric element, and depending on make/model, operate the Energy Cut Off (ECO) device. The ECO will shut off the LP Gas if that's in use, or open the electric element circuit if it's in the electric mode. Some ECO's can be re-set. BUT!!! Other ECO's are "One Time" meaning it has to be replaced for the heater to operate again. No cool-down re-set or manual re-set.
We had an Atwood Gas-Only water heater where he One Time ECO was part of the LPG Valve/Thermostat assembly. Part is around $100 and not all that easy to replace.
So... If you ever have to Winterize, You'll set the valves accordingly then remove the Drain Plug (Atwood) or Anode Rod (Suburban) to drain the tank so freezing won't burst it. Have a Spring Check List so you get the heater FULL of water again before powering it up.
