Hmm, I can't confirm this Behavior.
Two short Flights, one with the 4 Blade GNS and one with the 5 Blade GNS.
XP12.4.2-r2
AP did work as expected. HDG Mode, ALT Mode, NAV Mode with and without GPS, ILS Approach, all did work.
My Startup from Cold and Dark, no GPU connected:
Battery Switch ON
Inverter Switch to MAIN Position
Battery Isolation Normal
Avionics OFF
AP SBY Switch Light Green but no Action yet because Avionics OFF
Initiate Engines Startup Sequence with all the needed Stuff.
After Engines Start, Generators ON and Avionics ON.
AP SBY Switch Check -> All AP Lights ON.
Before Take Off -> No AP Mode selected, only Heading Bug and Target Altitude set. Flight Plan loaded. If there is one.
After Take Off and reaching the Altitude and best Speed for Climb and AP Activation:
- select HDG (stays green)
- select ALTSEL (green)
- select IAS (green)
AP ON
Yaw Damper ON
If a Flight Plan is active - Garmin CDI to GPS, AP NAV Mode enabled, GPSS Roll Steering Switch (GPSS HDG) to ON. And the Moo is happy following the Magenta Line.
So, no AP Mode selected while on the Ground, only in the AIR.
That did work since I purchased the Moo and with all XP12 Version since the first Release. Betas included.
Did you check your (new made) Joystick Profile for the AP Settings?
I use the Honeycomb Alpha and Bravo Devices with the Original Plugin and a simple Plugin Profile only for the Lights and the Rotators.
The AP Switches are Standard XP References and I can use both, the Buttons on the Bravo and the Buttons in the Cockpit.