Firstly make sure you are using the HDMI cable that came with your XSX for Xbox->TV, a 4k signal really needs a ultra high speed HDMI cable.
For Arc you must use the HDMI 2 to port connect to the Sonos (use the cable that came with your Sonos).
If that doesn’t help then check with Panasonic to ensure you have the latest firmware on your TV.
Firstly make sure you are using the HDMI cable that came with your XSX for Xbox->TV, a 4k signal really needs a ultra high speed HDMI cable.
For Arc you must use the HDMI 2 to port connect to the Sonos (use the cable that came with your Sonos).
If that doesn’t help then check with Panasonic to ensure you have the latest firmware on your TV.
I have already done what you suggested. But after a bit more digging it turns out that my tv (TC-55FZ950C) does not support Dolby Atmos… Which a massive punch in the gut. Thank you for your feedback.