Examine your breaker panels.
The most typical cause of furnace issues is when the circuit breaker that powers the furnace trips. Even if you have a propane or natural gas heater, you must first check the electric supply.
Check the settings on your thermostat.
If your furnace won't come on, the next step is to double-check your thermostat settings. If your furnace does not come on, make sure that your thermostat is set to “ON.”
Ensure that your furnace filters are in good working order.
To heat your house, your furnace needs a continual supply of fresh air. A filthy air filter can prevent your HVAC system from coming on by preventing the forced air system from supplying the heat pump with the necessary air to warm your house.