Squeezebox integration - no audio from Chromecast

Tags: #<Tag:0x00007fc4159d9078>

I’ve managed to get the Logitech Squeezebox platform working, playing music in response to commands. The only issue is that I don’t get any audio from my Chromecast, which is recognised by LMS courtesy of the excellent Chromecast Bridge LMS plug-in. LMS shows the track as playing on the Chromecast, but I don’t get any audio playback on the Chromecast.
Does anyone know the LMS/Squeezebox/HA architecture well enough to hazard a guess as to why I don’t get audio from the Chromecast?