I see it's been a while since this question was posed, and everyone has probably solved or moved on. Thought I would share my experience, because I have seen so many people with similar issues. It caused me endless amounts of time, and I hope it saves someone the same. I hooked my apple tv straight into my Anthem HDMI1 input and ran hdmi from the output to LG C3 oled. Great sound but could not get Dolby Vision under any circumstance. It also would not do 4KHDR, and 4KSDR was the best apple tv would allow. So, I went straight from the apple tv to the LG. Ran eArc back to the Anthem. Brilliant Dolby Vision picture, absolutely no audio. Fuming, and many many many hours later I believe I figured it out. Turning off CEC on both the Anthem and the LG (simplink CEC) with hard unplugging reboot of both. That simplink is a nightmare and repeatedly tries to turn itself back on and I believe remembers previous devices, so if you ever agreed to have it control your apple tv or your avr, it turns back on when those devices become active. From what I have read, I would be shocked if this issue did not occur with all types of sound bars and avrs. So, if you have problems with "Dolby Vision" not working or avr/sound bar "no audio" on your LG tv, turn off CEC on all devices. Reboot. Make sure CEC is still off. Try again. I bet it works.
