I don't see you mentioning if you can play music from the BS 9000 on the BL3500, but the subject suggest that you can't? One thing to check for first if is Masterlink is enabled on the BL3500 by pressing Menu, menu, 0, 9, GO with a BEO4 remote. Then you should be able to choose ML on or off with up and down arrows. If it is on you can also check the ML status by pressing Menu, menu, 0, 2, GO This will either show: NO ML, ML OK or an error 1-4. Let me know what you findings are

Thank you! I found the issue. Connected the Speaker to another Room. Works as expected. Seems I have a problem with the wiring in the junction box from where the cable goes to the place of the BL 3500.

Good to hear that it is working now. Always nice with an easy fix.  

Btw could I ask you to check the software version of your BL3500? It is done by pressing menu, menu, 0, 0, GO I have another thread where I am trying to find out which software versions that has been available, so just to see if there are some version that I don't know of. Thanks in advance

Took now a couple of weeks to dive deeper in my installation. I am not sure but I believe I faced an issue with my masterlink wiring. Unfortunately I have the cables in wall. I have mixed the old ML world and new NL world by connecting with a ML/NL converter. I bought a cable with a ML plug on one side and a RJ45 plug on the other side. Thought it would be good to connect to the converter. Cut this cable into two halfs in order to have to ends for connecting my devices and used a junction box to connect all 4 devices. The rooms with the standard old fashioned ML cable (9 wires) working perfectly, what means the BS 9000 delivers sound to the bathroom. The devices (BL 3500 and ML/NL converter) connected by the cable with the ML /RJ45 plugs are not working. The CAT7 cable provides only 8 wires and the ML cable provides 9 wires. I know the white / blue wire is bridged with the pink one. Could it be that the ML sense is not working without all wire on the dedicated pins. The BL 3500 shows no reaction (in the bathroom it is working properly) and the converter shows also no reaction. I hope my english is good enough that you understand my concern. :-) Thank you for your support.

The CAT7 wire should have a shield that according to the Beolink Handbook should be connected to the three solid blank wires in the ML cable. This is the 9th wire. hope this will help you

Thank you for the hint! The shield is not really connected to the blank wires. I will try to connect and give an update.

Unfortunately it was not the resolution. Must anything wrong with the cable and plugs or with the junction box. Checking the ML status I got the error code "2". For masterlink to work, must pin 3 and 12 be connected to the masterlink plug?