Your heat pump's internal computer chips are not communicating correctly because their configuration settings do not match each other.

Inverter not matched to Outdoor PCB dip switch setting

What causes this fault?

This fault occurs when the heat pump’s internal control boards are sending conflicting messages about how the system should operate. It usually happens because the physical switches on the main circuit board do not match the software settings on the inverter drive, preventing the unit from starting safely. This is typically caused by a component failure or a configuration error during a recent repair.