Do you use your phone for navigation in the car but find that while it works perfectly outside the car, once you’re in the car you stop getting audio from Maps? If so, does your car have Bluetooth that you use for calling? If yes, then here’s the likely issue. Your car recognizes calls and changes audio source to the phone. However, when you’ve got the radio on any input other than Bluetooth, such as Radio or CD Player, the car views the map audio as just another streaming audio stream and ignores it.
Likely, to hear Maps you’ll need to switch the input to “Bluetooth” or whatever the equivalent is called on the car, as if you wanted to stream music from your phone, and doing so will allow you to hear the maps audio.