The answer to 'why is my central air not turning on' is that there could be several common causes, such as a tripped circuit breaker, a faulty thermostat, or issues with the condenser unit. The most likely symptoms you may be experiencing are the air conditioner not powering on at all, the fan not running, or the compressor not kicking in.
If the issue is a tripped circuit breaker, you can try resetting it. If the breaker keeps tripping, there may be an electrical problem that requires a professional HVAC technician to diagnose and repair. For a faulty thermostat, you can try replacing the batteries or checking if the settings are correct. If the condenser unit is not functioning, it could be due to a refrigerant leak, a failed compressor, or other mechanical issues that would need to be addressed by a professional.