I have a 1 yr old A O Smith Gnr50-200. Water heater. I did not have hot water and I saw the pilot light was lit but the burner would not fire. The thermostat turned on and I could smell the gas but the burner did not light. I relit the pilot and the burner turned on. 3 days later no hot water again. Same thing relit pilot and burner fired up. Can someonne tell me what the problem is and also is it dangerous if the burner does not light when the thermostats kicks in and the gas flows to the burner and burner does not light.