Technically, I think, the mute button is part of Youtube not Chrome. Chrome displays it because it's part of the youtube page. When youtube switched platforms a while ago, many had trouble watching or displaying youtube vids. until individual computer were upgraded via Windows.
It might also be an upgrade issue with Chrome although I have never had a like issue with Chrome. Youy might check to see if Chrome has kept up to date. Click on the vertical three dots on top right corner of screen, then click on About. The updater for Chrome is there.
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