Why my speaker no sound?

Well I will suggest you to check for any physical damage in the speaker area of your laptop. Also check for the dust in the speaker, some time too much dust in are speaker can also cause these kind of issue so check for that as well. And try to update your audio driver some time an outdated driver can also cause these kind of issue as well. You should update the audio driver to it latest version, you can do it manually or you can try a good driver updater software like Advanced Driver updater or any other good driver updater software.