The answer to 'why is my central air not cooling' is that there are several common causes, including a refrigerant leak, a problem with the compressor, a clogged air filter, or issues with the thermostat or electrical components. Symptoms may include warm air blowing from the vents, the system running constantly without cooling, or the compressor not turning on at all.
If your central air is not cooling effectively, the first thing to check is the air filter. A clogged filter can restrict airflow and prevent proper cooling. You can try replacing the filter yourself. If that doesn't solve the issue, it's best to call in a professional HVAC technician to diagnose and repair the problem, as more complex issues may require specialized tools and expertise.