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 an issue with the indoor or outdoor unit. Some common symptoms include the system not blowing warm air, the compressor not running, or the system shutting off unexpectedly.
If your mini split is not heating properly, the first thing to check is the thermostat settings and ensure the system is set to 'heat' mode. You'll also want to inspect the air filters and clean or replace them if they are dirty. Other potential issues could be a problem with the reversing valve, which controls the flow of refrigerant, or a malfunctioning blower fan. These types of repairs typically require the expertise of a professional HVAC technician, as they involve working with refrigerant and electrical components.