Induction fan will not start when t stat call for heat and the l.e.d. on the hot surface ignition module is not lit, no code, good or bad

If I manually operate the safety switch behind the lower control panel door, the furnace fan comes on and moves cold air through all the vent for 60seconds and shuts off, same thing happens if I unplug the unit and plug it back in

I think it is a loose or faulty wire somewhere that I can't find, it's been doing this for a few days again and occasionally when I set the t stat to demand heat, the induction fan starts and the unit goes through the standard start up protocol, the last time I got it to come on, it lasted about 5-6 hours and I'm now back to no heat again

on a whim, I replaced the batteries in the t stat and the unit went thru the standard start up protocol and is heating the house fine at this moment, fingers crossed that it's not just a coincidence