American water heater won't light

I have an American water heater model number FG1F4034T3NOV that won't light. It started with the pilot light going out when the burner would go off. I took it apart cleaned the thermocouple, pilot tube and air vent and it still did the same thing. The thermocouple tested good but replaced it anyway and still the same. Then one day the pilot wouldn't light anymore so I figured it must be the gas valve so replaced that and still nothing. The thermal switch has continuity and bypassing it don't help, it has the new door with the flame lock system. I don't know what else it could be and can't afford a new water heater and my family needs hot water desperately. Any help is greatly appreciated, thank you in advance.