Odds are your Apple TV is plugged into the wrong HDMI port

Not plugging your Apple TV into the right HDMI port could result in a lower quality audio. Make sure it's set up right for ...
Ars Technica

Computer audio over HDMI into HDMI ARC input?

I've been trying to get my laptop to send audio over the HDMI output into the HDMI ARC input on a new amp. Didn't work with the 11yo v1.2 cable I'd been using but also doesn't work with the one ...