The answer to 'AC repair not working' is that there can be several common causes, including a refrigerant leak, a faulty compressor, or an issue with the electrical system. Symptoms may include the AC unit not turning on, blowing warm air, or making strange noises. In many cases, you'll need to call a professional HVAC technician to properly diagnose and fix the issue.
However, there are some basic troubleshooting steps you can try yourself before calling for service. First, check the thermostat to ensure it's set to 'cool' and the temperature is set lower than the current room temperature. Next, inspect the air filters and clean or replace them if they're dirty. You can also check the circuit breaker to make sure power is still being supplied to the AC unit.