Firstly, do you have an icon in your toolbar (bottom right of screen) showing a little speaker? Does it have a cross against it?
Look on your keyboard, right at the top - do you have a similar 'speaker icon' there too? When you press that, does the cross next the the toolbar go away?
Test the sound if it foes, to see if this has fixed it.
Be aware that some video clips on website have an automatic "off" - you'll see the speaker icon with a line through it or a cross next to it. Lack of sound in this case is their fault, not yours. You need to click on the speaker to activate it.
Then you can try this.....
Go to Settings and put "audio" into the Search box (if you haven't already tried).
Then click on Choose your Input Device (left side bar).
Check that the options given are really for the device you are using.
Then click on "Choose your Output Device'. and do the same.
Follow all the options for activating sounds - and I apologise if you've followed this route already.
I've just changed to Win 10, had the same problem and found I had to re-do the audio like this.
Let us know how it goes.