I have Win.10 using Chrome for browser, can get sound on everything but Facebook.
Consider this a blessing. Or try deleting your cookies and clearing the browser cache.
I’ve been beaten to the snark.
I would suggest trying FireFox to see if it works there. If it does, uninstall Chrome and try to do a reinstall. This will normally clear an issue like this up.
I have the same problem with some how-to YouTube videos. No sound on some but the next one down is fine. This is with Firefox and Chrome on both the desktop and my laptops. It is more irritating than a problem.
I have a different Firefox issue, all my browsers connect to the internet except Firefox based browsers. I have tried everything I know how to do, Chrome works fine and so does Edge.