I know this is a bit late, but in case you weren't able to fix it, I found something that might help. I had the same issues with my YAS-108 soundbar and my UN40MU6300FXZA TV; HDMI connected properly, CEC enabled on the TV, and the TV could even control the soundbar, but no sound. I verified that my TV's firmware had been updated to the latest version, and the issue persisted. I was able to fix the issue by updating the firmware on the soundbar to the latest version, and repeating the setup steps for the soundbar. I found Yamaha's instructions to update the firmware here: https://usa.yamaha.com/support/updates/yas-108_ats-1080_firm.html In case that link gets removed, just Google "YAS-108 Firmware Update" and that will get you in the right direction.
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