Right, this was the lack of my understanding that each ML-network built up "behind" the BLC also needs audio or video master on the ML-network representing the BL3500 which I agree then is easiest to fix by connecting the BL3500 to a BLC 1611. I've in the past always thought that one needed one primary A/V Master in the whole network but of with the BLC NL/ML I actually segment of a piece of the ML-network on it's on which needs to be powered. So the full connection chain will then be BL3500 connected via ML-cable to BLC NL/ML and then the BLC 1611 connected (via Master Link ML or RJ45) as well to the BLC NL/ML (which also could be a ML Power Box).

Got hold of 1611 which is not also connected to the BLC together with BL3500 which now makes the BL3500 react to the remote; good stuff! Next step is then to get the configuration correct and for now I don't get any reaction from other units; so something is missing and I'm kind of getting blind to what I've eventually missed. So the idea is then to be able to 1) pull audio from the BV10, Moment, etc., including being able to use the B&O app to play audio (Deezer) to the BL3500. Here is how the current config looks like:

You might want to set theBLC as A.master, V.Master or AV.master On the tab: “sources visible to ML” you will have to define what ML source names your BV10and Moment sources should have when controlled from the BL3500

Right, so since the BLC is it's own little ML it needs to have any of the A.master, V.Master or AV.master set and once I've done and tweaked the "Source visible to ML"; I could now play CD's from BS9000 and play cassette from BS6500. But, when trying to play TuneIn (Radio) or Music (N.MUSIC) from the Moment then the BL3500 quickly indicate source and then powers off (including that it also powered off the BS6500 stereo) all other units in the ML-network. To be mentioned is that the Beolink 1611 has fw 1.3 and whether that is an issue or not... So, half there 😀