Check to see if the pilot is lit. If not, light it per the lighting instructions on the water heater. If it lights but wont stay lit once you release the knob on the top of the gas valve, you may need a new thermocouple. if it is, turn the thermostat up. Its the big red or black knob on the front of the gas valve. Look to see where it is in relation to the mark on the gas valve. If it is in "vacation" position the main burner will not light and only the pilot will be on. If the marking on the thermostat knob is at "warm" or higher and the main burner doesn't light even if you turn it all the way to "very hot", the gas valve is junk. Most water heaters have a 6yr parts and 6 yr labor warranty. If it is a state water heater, their gas valves fail often. If its a bradford white, usually the eco (EMERGENCY CUT OUT) fails but if it does see why it failed before replacing the part as this is a safety and tripped because the flue is plugged. Unfortunately you'll have to call someone but at least is covered by warranty.
