The answer to 'why is my mini split not heating' is that there are several common causes, including a refrigerant leak, a problem with the compressor or reversing valve, or issues with the thermostat or control board. Symptoms may include the unit not blowing warm air, the compressor not running, or the system short-cycling.
If your mini split is not heating properly, first check the thermostat settings and ensure the system is set to heating mode. You can also try cleaning the air filters and outdoor unit. However, if the issue persists, it's best to call in a professional HVAC technician to diagnose and repair the problem, as mini split systems require specialized knowledge and tools.