Apple Carplay - volkswagen - music control

Hi,

I have been using Carplay via a wired connection to my iPhone X in my VW Tiguan, but recently I have not been able to control the music volume via either the phone or the cars entertainment system. Indeed, when listening to the radio, then navigating to the Carplay section of the car's system, the radio still plays through the car speakers, and music selected via the Carplay system comes out from the phone's speakers.

I have tried "forgetting" the car, and adding as new, but this seemingly did nothing.

Any ideas?!

George