I've retrofitted a used mk4 in place of my old mk2. The GPS antenna is set up properly and I can see the nav tracking my progress over the map. The problem is that the system won't route me to my destination. I'll input an address but the nav won't tell me how to get there. I'm familiar with how a mk4 operates so I'm pretty sure it's not user error. I used NavTweak to read the system parameters and then update the nav with my car's details. None of that made a difference. Do you have any ideas what to do next?