The answer to 'mini split not turning on' is that there can be several common causes, including a tripped circuit breaker, a problem with the outdoor unit, or an issue with the refrigerant charge. First, check the circuit breaker and reset it if it has tripped. If that doesn't work, the outdoor unit may have a problem with the compressor, fan, or other components. Additionally, low refrigerant levels can prevent the system from turning on.
If the issue persists, it's best to call a professional HVAC technician to diagnose and repair the problem. Attempting to service a mini split system without proper training and equipment can be dangerous and may cause further damage.