Cannot connect the Android Auto app to the car stereo

There is a possibility that the setting of the installed Android Auto application does not allow Android Auto connections.
Check the following settings.

1. Start the Android Auto application, and then select Settings from the menu on the upper left.
   
2. Select Connected cars.
3. Set Add new cars to Android Auto to ON.
   
4. If the device is included in the Rejected cars list, delete the device from the list and add it again.