Been having the same issue with a Bose soundbar plugged in the eARC. It was working flawlessly up until two weeks ago. But now the sound does go through but no way to change it with the remote. CEC control also shows inactive. That sucks. Been planning on upgrading my Roku but staying with them but now I'm very hesitant after reading through this thread
Thanks! Did all that you suggested multiple times, and the result is still the same. So, I gave up and went and got new equipment. Now things work, as intended, although not perfectly. ARC & eARM has some issues with their compatibility with equipment from different manufacturers that's frustrating customers and needs fixing.
Make sure the HDMI Cable says "Ethernet"
I hope this helps at least someone, my vizio soundbar that has been hooked up for years and working fine decided to stop allowing volume control but it still worked at the last volume and via soundboard remote. It wasn't showing up in cec and volume control was inactive.
After a bunch of trial and error. What I did was unplug both the soundboard and tv from power, while still connected via eArc and pressed the power button for 15 seconds on both tv and soundbar to drain out any residual power. Plugged them both back into power and miraculously it worked immediatley
Thanks for trying but the soundbar has never worked though earc . The soundbar worked perfectly on my old Roku tv (that died) . Case open with Roku and nothing after a year!!!!!!!!