1st, we have no idea what device you are talking about.
2nd, most devices, by default, disable onboard sound once headphones are plugged in. If you think about it, that is the point of headphones.
If you are not getting sound period after you plug in your headphones, it's possible your headphones, if they also have a built in mic, has the pinout setup in a way that doesn't like the device you are using, but again, we have no idea what you are using. a laptop, desktop, phone? what brand/type/model of laptop, desktop or phone? Contrary to popular belief, we aren't all psychic
