@
5hairpins, I would verify the connection at the Harman Automotive extension box and at the USB/aux connector. I read on another forum where the problem you are having was due to a unsecure connection. The post stated they realized that was the case when they tapped the area near the USB/aux plug and the signal would return intermittently.
My issue is due to me reconnecting the USB connector into the wrong port.
2014 6-speed Monogram (37J)