No sound when playing Spotify Connect on Volumio with Snapcast client

Hey all,

I have the following setup:

Pi 3 - Snapcast Server (no client)
Pi 4 - Snapcast Client (HDMI)
Pi 0 - Snapcast Client (HifiBerry DAC Zero)

On each Pi:
Volumio 2.917
Snapcast plugin v2.5.1

When playing Spotify Connect on the Volumio instance running the Snapcast client, there is no sound at all.

Playing music on the server correctly makes it play back on the clients, but I need to be able to do individual playback on my clients as well.

Settings on the clients (only difference on Pi Zero is the DAC):