I went to fire up my fireplace that has been running great for the past 3 years (only difference this past summer is I shut off the pilot). I pulled the remote to start the pilot and it fired up just fine. I clicked on Flame and I don’t get anything, no flame. I can hear the unit operating to raise and lower the level of the flame, but get no flame. I allowed he pilot to run for several hours but still couldn’t get it to fire up. I pulled all the logs out, cleaned (sanded) the thermopile, used a compressor to blow out any debris, but still no flame when it calls for flame. Pilot is strong, blue flame. What am I missing?