Spotify only not working in Volkswagen Touran 2006 when using iPhone X(s)

[concourseb]

I have a Touran 2006, without bluetooth, but with USB/Aux ports. The display/audio works completely fine, through USB, when I use Spotify on an iPhone 7 or iPhone 6. But for some reason, iPhone X (and iPhone 8 too) doesn't work. Nothing comes up on the display.

I have tried with three iPhone X's and all other phones mentioned above, but only iPhone X (and iPhone 8 ) don't work. I have an iPhone XS  and there must be something wrong with the software of either the car, phone or the app.

I have updated iOS and Spotify premium. 

What can I do to make Spotify work in my VW Touran with my iPhone XS? It makes no sense that it wouldn't connect.