no power

Hi, I have a 10 year old Lennox furnace that stopped working overnight. Tried swapping thermostat with an identical functional one, nothing. Green led on board does not light up at all. It is getting 109 volts at the control board but the moment you plug in the 24v transformer, it drops to 0.1...

My honeywell wifi thermostat went blank while my heater was running yesterday and now I can't shut off the heater unless I unplug the York furnace. Here's what I've checked so far but still can't figure out what's wrong and the cause of my blank thermostat. Would appreciate if anyone can give...