Do other gas appliances work? Did you just turn on the gas? Slowly? Do you have adequate battery power for the circuit board. Ours will not operate even if plugged in if the battery is not good. Does your water heater have an on/off switch on the heater itself that has to be turned on? Inside switches for gas and electric? Should be able to use one or the other, or both at the same time. Forgot to mention, I can also only get warm, not hot water if the showerhead is shut off with the showerhead switch and not the main faucets, same goes if an outdoor shower is shut off that way. Check those too.