Hi, I was able to resolve the problem a few days ago.
When you turn on the car it will ask for a code. Put in your NAV system code.
Once it accepts, press the left dial to turn on your radio.
Look up at the LED display where your clock is... Notice it will now say CODE.
Twist the knob, I forget if it is the left or right knob... And you'll see numbers move from 0-9.... Twist the knob to the number you need, press the knob in and then it will move to the next digit.... Do this to put in the 4 digit code for the radio.
I hope this helps!