Do the wired Skullcandy Crushers work on any other known working audio devices? By "work" I mean will the slider change the bass if the earphones are used on another device?
Do any other known working, bass adjustable earphones work on your computer/audio device?
Determine if the problem follows the earphones or stays with the computer/audio device.
If computer, right click the small speaker icon usually located in the lower right screen corner.
A menu window wiil appear with multiple choices leading to all sorts of other audio related screens, windows, tabs, and properties.
Try the troubleshooters first.
Failing that, take a look at the other menu choices and options.
Do not make any immediate changes, explore first and keep notes as necessary. Then make changes as may be warranted. Change only one thing at a time.