When you first realize there's an outage in your HVAC system, start by checking your circuit breaker to see if a tripped breaker caused the issue. If the breaker is fine, check the thermostat settings to ensure they're correct. Next, inspect the air filter for blockages and replace it if necessary. If these steps don't resolve the problem, contact a professional HVAC technician for further diagnosis and repairs to restore your system's functionality promptly.