Your vizio tv maybe a smart tv, but the roku soundbar is too, it only controls apps on the roku soundbar home page, you need to have it set to the hdmi input the roku soundbar is connected to, then use roku soundbar remote to control the apps. If you have it connected to the right hdmi the one marked arc, you can then hear audio from other devices connected to your tv through the roku soundbar.
If you want to use the roku soundbar for better sound only, stop using its remote, use the Vizio remote and then you'll have control of the smart apps built-in to the vizo tv. But with better sound. You'll have to pick.
Edmund
Roku Community Streaming Expert
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