Great to see your setup working now. I’m in a similar situation — I’m also using Halo as my primary way to control the volume and sources on my Beosound Core connected to my Beolab 50s. It’s a very convenient setup once everything is synced properly in the app.
Is it a Beosound Core (old) or Beoconnect Core (new) you have? I have Beosound Core and Beolab 50, where I have the Core’s optical output (line/optical combo 3.5mm jack) to the Beolab 50’s optical input.