I have a Sonos Arc connected to a Pioneer PDP-LX508a Plasma.

because of the age of the TV it does not have ARC and will not pass HDMI audio through to the optical out it will only pass it through analog….strange I know.

for me to use the Sonos Arc I had to use one of those small analog to digital converters with optical out and connect the optical using the Sonos optical to HDMI converter ….this worked a treat for the last 12 months until the last day or two, it stopped passing the audio.

i have tried everything to find the problem and the only thing I can come up with is that Sonos has done an update and it’s broken the Sonos optical to HDMI adapter …..but

I  have a work around for it !!
I had an old ZP80 lying around not doing anything 
So i noticed it had an analog line in and an optical out.
I fired up the old S1 app and connected it to the network, then I selected line in, connected the analog out from my TV and connected the optical adapter to the ARC and sound !!
So until it gets rectified I will be using my old ZP80 as a analog to digital converter