I have found a bug in MC 20 related to zone setup.
I hadn't noticed this.
I did have a Zone I made for my bluetooth speaker last weekend (as a duplicate of my regular Zone), and I had some trouble with it. But, I'm not sure this is exactly what I was seeing.
I had to re-set
Tools > Options > Audio > Audio Device on the zone after I used it the first time and I'd turned off the bluetooth speaker. It worked all evening, but then the next day when I went to use it again, I had to re-select the Bluetooth speaker as the Audio Device (even though it "looked right" in the options panel). When I played to the zone without doing this, it didn't error or anything (and appeared to be playing) but no "music happened".
I assumed this was because when the bluetooth speaker reconnected, the OS assigned it a different index or something, and so MC's Zone didn't point to it correctly anymore. It is possible, I suppose, that the change I made to get it working in the first place didn't "save". But, I don't think so, because I had to do DSP correction (my speaker will only play 44.1kHz audio, so I had to set MC to resample everything else), and that saved. Hmmmm....
I didn't notice if the duplicating the existing zone worked right, but I didn't encounter any problems. I
think it did, but I'm not sure.