The answer to 'my tune-up won't turn on' is that there could be several common causes, including a tripped circuit breaker, a malfunctioning thermostat, or an issue with the HVAC unit itself. Symptoms may include the unit not powering on at all, strange noises, or a lack of airflow.
Some basic troubleshooting steps you can try yourself include checking the circuit breaker, ensuring the thermostat is set properly, and verifying the unit has power. However, if you're not comfortable working with electrical systems or the issue persists, it's best to call a professional HVAC technician to diagnose and repair the problem.