No hot air coming out of vents?

If no hot air is coming out of the vents, it could be due to several reasons. Check the thermostat settings to ensure it's set to heat mode and the desired temperature is higher than the current room temperature. Additionally, inspect the furnace or heating system for any issues, such as a pilot light that may be out or a tripped circuit breaker. Lastly, ensure that air filters are clean and that vents are unobstructed for proper airflow.