The answer to 'why is my air conditioner not working' is that there are several common causes, including a dirty air filter, refrigerant leaks, electrical issues, or a malfunctioning compressor. Symptoms may include the unit not turning on, warm air blowing, or the system short-cycling.
If the air filter is dirty, try replacing it. If you suspect a refrigerant leak, call an HVAC professional to inspect and recharge the system. Electrical problems like a tripped circuit breaker or faulty thermostat may also be the culprit. In some cases, the compressor may have failed and need to be replaced, which is best handled by a certified technician.