Nav system intergration with HUD
 

I just purchased a new 2006 C6. The Nav system is supposed to give turn commands that are repeated in the HUD when it is in the street mode. It's not happening. Two dealers have been unable to analyze the problem even with GM tech. help. Has anyone had this problem and ,if so, what did it take to correct it?
Everything else on the car works great. Thanks for any input.