Why aren't my headphones working in my laptop?

I plugged them in & they didn't work. So I tested them through the control panel (sounds folder), it said they were working correctly. I retested them with a youtube music video and they are still not working. The sound is playing through my speakers on my laptop, not through the headphones. My fiance has the same laptop (just a different color) and they work fine in hers. Can someone help with whats going on?