The answer to 'why is my air conditioner not turning on' is that there are several common causes, including a tripped circuit breaker, a faulty thermostat, a clogged air filter, or a problem with the compressor or other internal components. The symptoms you may notice include the unit not powering on at all, the fan not running, or the air not blowing cold.
For simple issues like a tripped breaker or clogged filter, you may be able to troubleshoot and fix the problem yourself. However, if the issue is with the compressor, refrigerant levels, or other internal components, it's best to call in a professional HVAC technician to diagnose and repair the problem. Attempting to service the air conditioner yourself could be unsafe and may even void the warranty.