What are you using for the destination and start? There are radio buttons for Use GPS location, Use end of route, and for inputting an address. If you leave the radio button for one of the others set, you can't put in an address, you're still telling it to use whatever is checked. I think Use end of route is the default, and if you don't already have a route, then you can't use the end of nothing. If you don't have a GPS connected, you can't use that, either. To give it an address, you need to set the bottom button, Origin, and then fill in the address.