Cannot use airplay

My appletv 4 sends audio to an aiplay speaker. All apps work fine except channels.
When I open channels it either plays the video with no sound or annonces that the connection to my speaker has been lost, the the audio reverts to appletv built-in (over hdmi).

Tried everything I could think of :

  • reset my speaker to factory default,
  • rebooted my appletv
  • uninstalled then reinstalled Channels

nothing worked.

I got a refund from Apple. I’d love to know when the problem gets fixed.

What kind of speaker is it?

Riva Arena.
Works just fine with all other AppleTv Apps (plex, molotov, etc.)