Caravan Autopilot Not Capturing Track in Nav Mode with GTN750

Hi I’m hoping someone may have encountered this before:

With a simple GPS route loaded via the GTN750 (from the toolbar) the route displays ok on the G1000 NXi however when flying a heading intercept or manual intercept of the GPS track the NAV mode fails to capture the track and flies straight through it even at a very shallow angle.

Is the because I have the PMS50 GTN installed? Or might there be another reason. For clarity the CDI was set to GPS on both the 750 and the PFD.

Any ideas?
Thanks