The answer to 'ductless system not cooling' is that there could be several common causes, such as a refrigerant leak, a problem with the compressor, or a clogged air filter. Symptoms may include the system not blowing cold air, the compressor not running, or the system short-cycling.
Some potential solutions include checking and replacing the air filter, inspecting the outdoor unit for debris or damage, and verifying the refrigerant charge. However, many ductless system issues require the expertise of a professional HVAC technician, especially if the problem involves the compressor or refrigerant system. It's generally best to call a qualified technician to diagnose and repair a ductless system that is not cooling properly.