An update on my 4yr old 19"vizio.. I used the
Turn off method and it worked a few years ago. No sound again years later. The turn-off method did not work after several attempts.
BUT I plugged headphones into the TV to see if there was any sound... there was with the headphones, and when I disconnected the headphones from the TV, the sound came back on! Who knows why, I certainly do not. Just know it works and it's a way to find out if there is audio.

THIS TOTALLY WORKS!! I was freaking out because my husband does not come home for another 48 hours (Firefighter) and I wanted to be able to watch TV so I looked up "No Sound Visio TV" and your suggestion WORKED!! Thank you so much for helping me do this on my own without calling the hubby at work. :-)