If the thermostat tests out good and the burner still does not light, the Hi Limit may be tripped. The reset button is located on the back side of the control box. Locate this button and press it in. If it is tripped, there will be a click when it is pressed. This will have it reset and allow the burner to work again. If the Hi Limit does not move in or does not click, it was not tripped.
The HI LIMIT for these is located on the back side of the control box.