You may need to perform a few tests around volume so we can isolate the problem.
Video sound setting: Video may not have sound because sound has been turned off on your computer or the video - Hover over your speaker icon on the video and see the level of volume. If this is high then check your computer's sound.
Sound card: Go to another site to see if there is sound for other online videos. This is for your sound card verifying. If all videos have sound except for the tutorials then your sound card has nothing to do with it.
Different browser: You can also try to test the audio by using different browsers which may be the solution.
Important steps to follow:
Make sure your browser is up to date.
Try playing the videos in incognito mode.
Clear cache and cookies for your default browser.
Use any other alternative browsers (Chrome, Firefox, Safari, Opera, Edge).
Check your laptop/computer audio settings.
Play content on a different device.
Restart your laptop/computer.
Run our system test.