Autopilot issues after GTN750 install

I’ve installed a RealityXP GTN750 and 650 in my vFlyte Air Twin Comanche (X-Plane 12, Windows). They seem to work well but for some reason the approach and nav functions of the autopilot are not functioning properly now. Heading mode works and responds correctly to heading bug inputs. However Nav and Approach modes don’t work properly. They seem to just hold the current track when selected on, ignoring any CDI guidance. I’ve tried in both VLOC and GPS. Any ideas or help would be greatly appreciated. Thanks in advance.