Hey, I believe you just need to tell pulseaudio where to find the dbus socket, detailed here: https://www.balena.io/docs/learn/develop/runtime/#dbus-communication-with-host-os
You could set DBUS_SYSTEM_BUS_ADDRESS=unix:path=/host/run/dbus/system_bus_socket in the environment section of the pulseaudio service, and this should fix your issue.