The answer to 'why is my ductless system not turning on' is that there could be several common causes, such as a power issue, a problem with the remote control, or a mechanical failure. The most likely causes are a tripped circuit breaker, a dead battery in the remote, or a malfunctioning component in the ductless system itself.
If the system is not receiving power, check your circuit breaker to see if it has tripped. Reset the breaker and see if the system turns on. If the remote is not functioning, try replacing the batteries. If those basic troubleshooting steps don't resolve the issue, it's likely a more complex problem that will require a professional HVAC technician to diagnose and repair.