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 thermostat issue, or a problem with the air conditioner unit itself. The symptoms you may notice include the system not powering on, the fan not running, or a lack of cool air being produced.
Some potential solutions you can try yourself include checking the circuit breaker, replacing the air filter, and ensuring the thermostat is set properly. However, if the issue persists or you're unsure of the cause, it's best to call a professional HVAC technician to diagnose and repair the problem.