See my comments in your other post earlier. YouTube video link there explaining how to remove the Sail Switch. Start by blowing out the furnace compartment with a blower to get loose dirt and dead bugs out. Flip the reset button. It should fire until it faults again. Once it faults, check the red flashing light on the furnace board. See the codes I put in the other thread you started. Depending on the type of flash will determine the problem. Sail Switch is very easy to get to and cleaning off lint and dust will probably let it work again. Reassemble, flip the reset switch again, and see if it cycles correct. If it does, replace cover and enjoy the heat!
FYI, when I did mine at 11:30 pm last night, I did not unplug power or disconnect batteries. Just handle carefully and don't touch any ends of wires.