no headphone output

hi all , i am haven problems with my new mixvibes home7, i can play tracks and the sound comes out the speaker on my laptop but when i click on the headphone switch to cue up a mix there is nothing coming out of my headphones it just comes out the speaker along with the existing track, i have tried it on both chanells and switch the usb sound card to diffrent ports but nothing, the only sound i get is the windows sounds if i click on the volume control for windows it displays 2 diffrent channels but still no music coming out , i no its going to be something simple but would relly like some help hear , thanks