My Lenovo laptop stopped playing sound?

I just got a new Lenovo laptop about a month ago. Then today I went to watch a video and nothing happened. The video played but no sound. I then tried other sites and still no sound anywhere. Everything is set to full volume but there's still no sound. I even turned off the computer and restarted it but it didn't help. Also nothing plays with headphones either. I don't know what to do.