Look for leaks. Perhaps over heated connections (plastic plugs will brown).
I’d also check your smart plug (assuming it’s smart rather than just a timer), and see how long it was on before it decided to “trip”. My tapo plug shows the power draw on a time Vs power graph.
Might give some clues!
Does it have an auto off safety feature if any conditions aren’t met? I.e water tank too low, could be a dodgy sensor for example?
I’d be logically going through all of the circuits personally.