I recommend printing out Part III Normal Procedures in your documentation.  (You may have done this.)  It is a fairly detailed guide.  (You may have done already.)

This is not a simple airplane.  So it is possible that you are missing a step.  It is also possible you have a bad installation.  So the fixes range from filling in a missing step all the way to uninstalling and re-installing FSX.  Without being able to look over your shoulder, it is hard to say what the problem is, unfortunately.

If you could provide a step-by-step description of everything you are doing, that might help, if it were complete enough.  Screen shots would be better.  There's just no easy way to do this, I'm afraid.

It is frustrating that people are experiencing the airplane not following routes when I know darned good and well it can.  I will try to do a quick and dirty tutorial of how I do things, since at least it works for me.