So,
I have just introduced myself and thought it would be ok to submit my problem. I hope someone has some experience with this and you can help!
As I said in my introduction, I have a 2004 v50 with the premium sound system and a single cd-player. I wanted to plug something into the aux, which it didn't have. I therefor bought me a Dension 500 gateway. Sadly it won't work. I have used he following instruction from the manufacurer.


The dip-switches are correct I have 1, 4 and 6 on.
The most-ring is complete, since the aux shows a blue light that is constantly on.
When I put it in service mode, both my cd-player and my radio work perfectly fine.
Also, all my dashboard functions work like normal.
I should say that it's second hand. However, the previous owner promised me it worked (I may be somewhat naive, but I trust this person). So for the sake of this thread, let's assume the gateway works well.

Is there anything I missed or I'm doing something wrong?
Thanks in advance for any help.