I would guess there is no power to the thermostat and the furnace control board. First check the circuit breaker in your main panel box to be sure there's 120v AC getting to the furnace. Be sure the furnace on/off switch is ON. Next, if you have 120 volt power, look on the circuit board that's inside the furnace for a small (~1"long, 1/4" diameter cylinder shape) fuse. See if that's blown. If that fuse is blown then we need to determine if it blew due to a freak happening or a real problem. Make and model of the furnace will help.