As an AV installer, I’m getting a lot of service calls for this exact issue. It’s happening between various models of Samsung and LG TVs as well as Roku models (Express, Stick, and Ultras). We simply unplug the HDMI from the Roku and then the soundbar ARC works as expected. Roku needs to dive deeper into this. It’s a repeating, reoccurring issue. I feel like the Rokus are trying to communicate to other HDMI devices connected to the TV or it’s something with HDCP. Sometimes swapping HDMIs work. Sometimes switching sound output to stereo or PCM helps. Other customers are left with unplugging and plugging the HDMI out of the Roku device to get their soundbar going.
