Any luck on your side? I am experiencing exact same issue but with JBL speaker.
The TV reconigzed the TV and OSD appear when volume button pressed but no change on speaker.
I tried to use optical instead of HDMI and still does not work. However, if I connect the sound bar via Bluetooth the control works!
The samsung tech agent said on call the issue likely because the speaker might not be compatible which I dont believe the case.