Just to ask again. Are you loading your FSBuild flight plan via the FS Flight Planner?

E.G. I create a plan using FSC9 (like FSBuild) save it to the C:\Users\USERNAME\Documents\Flight Siumulator X files\xxxx.pln. Once I load that flight using the default FS Flight Planner, I can follow that plan using the A/P in NAV mode. I don't kmnow if it has anything to do with the Nav/GPS Switch.

Mark