Got a Kenwood DDX374BT and recently bought a new phone(Motorola MotoZ3) and Bluetooth audio and charging work fine but when I try to play music through the USB I get nothing.
Things I've tried....
In phone,turned USB debugging on.
In phone,switched USB configuration setting from "no data transfer" to "file transfer".
Turned radio on and off,etc.
Tried a different cable.
Had no issues with my last Droid Turbo,not sure why the radio and phone won't communicate through the USB port??