Autopilot will not turn on

Pressing any button on the autopilot causes an instantaneous reset of trim to the 0 setting and the autopilot turns off immediately. I have attempted this both thru pressing the button in the 3D model and using an assigned button: the effect is the same. This includes pressing buttons that should do nothing (like ALT or NAV) even though the autopilot is off.
Is there a work around?
I am using the TDS GTNXi option with the plane.

Hello,
Read the provided "User manual" , to understand the tests to do on the ground to make it work
> On the ground , you need to put the button on test until 2 yellow and green light are flashing.
> Then you need to put it ON

You can also read the full Auto pilot manual on provided "Flight manual"

Regards