I have an A8H that works with ARC on my Denon 4300, just put a an Arc SL in place as I’m moving the Denon to a dedicated theater.
I’ve unplugged everything but the ARC from the A8H and have yet to hear any sound out of the Arc via the TV ( I did proof of life with Spotify), every time I get to the testing phase the Arc says “Audi System Not Connected”. I switched from my HDMI cables to the ones that come with the Sonos, I’ve powered everything off and unplugged, called Sonos support who walked me thru the same things I had already done and suggested I call Sony (that was a short call when I mentioned the Denon works on arc like a champ).
Arc and TV are connected to WiFi, WiFi is Ubiquiti networks.
Any Ideas?