Exactly – you cannot have the AP “ON” when the plane is not flying, as it cannot control the plane, and will typically run its controls to limit.
The only exception, is if you want to TEST some of the AP functions when on the ground. ie AP Heading operation, where, (if you have a FF Yoke/Joystick", you should see movement on the control, as you submit a AP heading deviation command etc etc)
Also, MAKE SURE that the AI Pilot is OFF, unless you really intend for him to take over flying the plane, AND over-riding the AP.
I suspect that MANY of the AP not working / crashing the Plane reports, are from “Pilots” who have left the “AI Pilot” turned ON !!!