I'm curious as to whether it tries to light at all or it tries and fails?
I ask because I replaced the thermostat in mine recently. The old thermostat was bad and it would heat the water up until the high-temp cut-out kicked in. The pressure from the steam was causing all of my hot water lines to leak!
Anyway, now that I've replaced the thermostat the heater will heat up like it should, but not always turn back on when it needs to. BUT it tries. The red light comes on which I think means that the thermostat is working, but it's failing to light. I'm wondering if it's possible to get a "bad batch" of propane? The fridge is acting up, too, after having recently refilled the propane tank. It takes several attempts to stay lit, but once it's lit it stays lit.