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found the answer in another forum 

nothing to do with fsnav, the aircraft just wont let it on its own, its gotta follow the FS gps  oh well, VOR to VOR it is

Start FS9 and go to the "settings" on the menu page. Select "Controls/Assignments" then select "Radio Commands". Scroll down to "Nav1/GPS on/off" and assign the 'N' key to this.

After doing your FSNav plan and saving it to FS2004 and load it into FS2004.

Once in the aircraft you should see the plan in your GPS Screen.

Take off and using the heading bug or hand flying, get onto an intercept heading to the course line shown. Then turn on the autopilot and press 'N' . You will only see a change in the course deviation bar on your HSI, showing displacement from the GPS course line.

Select "Nav/Loc" on the autopilot selector, and the aircraft will turn onto and track the course when intercepted. It will continue to track the course, through changes at waypoints, all the way to your destination, until you either push 'N' again, which will return the A/P to VOR nave mode, or turn off the autopilot.