Pro tip: after cleaning the shmoo off the thermopile, ensure you turn the knob back to "ON". Troubleshooting steps: 1. Turn off the pilot. 2. Check and clean the thermopile and thermocouple. They heat up and provide electricity to open the gas valve. They don't work if the shmegma buildup is too thick. The thermocouple provides electricity to keep the pilot light valve open. The thermopile provides electricity to keep the main valve open. This is for safety; if the flame gets blown out, the gas valves will shut off. 3. Make sure that the wall switch - fireplace on/off is working with a continuity check. 3. Turn the pilot back on. If that didn't work, call a gas fitter.