Spotify won't connect to chromecast audio group

[lisbong]

I've got two chromecast audio decives set up individually and as a group. If I select either device individually Spotify casts perfectly however if I select the group it just hangs 'connecting' forever.

I've checked the router and the AP client settings are ok. I've rebooted the devices and the router. I also deleted the chromecast app and the Spotify app. When I reinstalled the Spotify app it did connect to the group once but then hasn't since. I deleted and reinstalled the app again but this time it wouldn't connect.

Also, the Tune in radio app casts to the group without issue so I don't think there's an issue in the setup. It seems something to with the Spotify app?

Is there anything I can do to get this to connect?

[lisbong]

Sorry posted in the wrong forum. Re-posted in iOS forum