Get back here so we know we are not wasting time.
When the thermostat kicks on, that demand will immediately turn on the indu ction fan in a forced draft system. The fan will run for X time and a press ure sensor will tell if there is a pressure buildup in the flue.
However you are not even getting that far. If the induction fan never turns on, it could be the thermostat itself. You could just short the wires when it doesn't work, if it does then, it is the thermostat. If it doesn't, it may be the control board. Though the induction fan is the first thing to tu rn on when the demand is called, it is not directly connected as it would b e in a normallt aspirated flue system. It goes to the PC board. This is bec ause it remains runniing for a short time after the demand it met. There is a timer involved.
When it doesn't work, short the wires to the thermostat out and see if it d oes.
J