If the pellet feed auger screw is empty, then you must press the load (PRIME) button manually and that turns on the LED Yellow light. This is to make the initial filling of the screw, even when one observes commence of fall of pellets to the burner.
Power Initialized: If POF open, unit enters initial cool down mode (approximate 9-min). If POF is closed, unit will begin a Warm Re-Start to IGN.