The answer to 'condenser not working' is that the condenser unit, which is the outdoor component of your HVAC system, has likely stopped functioning. This can be caused by a variety of issues, including a faulty compressor, fan motor failure, refrigerant leaks, or electrical problems. Common symptoms include the unit not turning on, the fan not running, or the compressor not kicking in.
Before calling a professional, you can try some basic troubleshooting steps, such as checking the circuit breaker, ensuring the unit is receiving power, and inspecting the condenser fan. However, if the issue persists or you're not comfortable working on the HVAC system, it's best to call an experienced HVAC technician to diagnose and repair the problem.