I signed out of the app, removed it, unplugged the TV, waited 10 seconds, plugged it in, reloaded the app, signed into my provider. No sound. Even stranger... some, not all of the commercials play sound. All of the recorded sessions have sound. Just not the live stream. This doesn't seem likely to be a problem on the device end.
Channels on Roku are maintained by the channel developer themselves. If the issue only occurs on CNBC, we would recommend reaching out to their support team to report the issue and get help. There's likely an issue within that specific channel that needs to be addressed with an update from the channel developer.