The pinouts for Symphony II+/Concert II quadlock are VERY slightly different from the RNS-E (the Symphony/Concert variants communicate through the K-Line, but the RNS-E uses the CANBUS. Need to move a couple of pins around to make it work.
Basically need to do the reverse of this guide:
https://www.motor-talk.de/forum/aktion/Attachment.html?attachmentId=700217
Much simpler than it looks at first glance, and even easier if you don't have Bose!