OK, I woke up this morning after our first REALLY cold night, and no heat.
I turned the heater off and on, it sounded like it was trying to start, but no dice. The fan will kick on for a minute, and then shut off. After some research, it seems like maybe a dirty flame sensor is a common cause, but I can't seem to find it. My model has an enclosed burner apparently?
I am getting a few different types of LED flashes - first 3 long flashes, then one long and three short. There is no listing of error codes on the door to my furnace.