Best answer by Ryan S - Sonos
We don't have a recommendation here for a specific mixer to use for this setup. That FCA610 you have might just need to have the settings configured, so please make sure that the optical output is set to play the optical input.
Just to make sure it isn't a problem with the source, try wiring from the TV directly to the PLAYBAR and see if you hear the audio.
You can give us a call and a technician will be able to assist live.