Ever since ~11aug 2024 spotipy (the library handling the playback API) has been unable to find/connect to the Spotifyd (the library actually playing back the sound) process.
It will work without issues if you manually connect to the Speaker from a mobile device, as the SpotiStation will still be listed as a device there. But for whatever reason, the SpotiSation device no longer shows up on spotipyd.devices. It still seems to be logged into the user that credentials are provided from.
At this point it is not clear which library is the problem. Spotipy would be the culprit as the deamon process is running and it works as expected from mobile devices - but I cannot rule out something changed on the authetication from Spotify that somehow makes the deamon process no longer listed as a "device" in the API unless they are connected to manually.
This is further corroborated by the fact that around aug 11th there seem to have been issues regarding authentication affecting Spotifyd and other libraries. These issues may well be connected.
For now I don't really see an easy way to fix this. If this is affecting your device, please get in touch - I will spend more time looking for a solution.