While switching channels TV sound suddenly stopped & it will not come back on. We have checked & its not on mute; turned TV off & back on, with no results

1) If you have an HDMI cable going to your second input (or have wireless connection such as Chromecast), switch to that and use Netflix or cast a radio station or something to see if you have sound.
2) If you do, check the HDMI cable from your TV to the cable box, and check the power cord while you are at it. ANY connector between TV and cable box.
2a) If you don't have secondary inputs, just check all connections a few times. If that doesn't work, disconnect cable and power to the cable box, wait 3 minutes, plug back in, and try again.

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