Autopilot will not follow GPS

[Rymrks]

Hello Pete,

Can you please give us some more details on how you experience this problem? The GTNXI should work with NAV mode, provided that the airplane has a proper NAV mode/autopilot.
Also, with which airplanes have you tested the autopilot without success? Does it work with any one?

I am having the same problem using the JF Arrow III and the TDS GTNXI 

It works pefectly with the PMS 50 which I have removed also from MSFS but not with the TDS GTNXI

Roy