I can't hear any music playing from my Spotify Connect speaker (Libratone Zipp from 2012) and I'm wondering if something changed today in the Spotify Connect protocol or streaming format?

I see the speaker listed as a Spotify Connect destination when using the Spotify app on iOS or Mac Desktop. I can select the speaker and the app behaves as if everything is fine; the progress position moves along and I can adjust volume. The speaker comes out of standby but no music actually comes out it.

I have tried restarting the speaker and have confirmed that it plays back fine using AirPlay. But Spotify Connect seems to have stopped working.