You have 2 issues.
After market hot rod is NOT connected to/thru anything OEM on that water heater.
It has it own AC Power and t-stat controls.....either it is burnt out due to no water in WH tank, it-s t-stats have tripped (not reset) or the outlet it is plugged into is dead
Propane not working......
DC feeder fuse bad
DC Fuse on circuit board bad
Thermal fuse blown (brown wire-----clear tubing)
ECO T-stat tripped. But it will self reset water temp cools to roughly 110*F
You do get water flow out of water heater tank HOT side.....correct?