Hey this is Jim with Crucial Vacuum,
If there's no noticeable debris on the brush roll try manually rotating it to help unearth any hidden clogs behind it. Take note of the condition of the bristles while you're doing this. If they look worn down, or loose then its time to replace your brush roll.
Check your vacuums belt as well. Overtime your belt will stretch and loose resistance. This could lead to the brush roll no longer turning. Be sure your belt is on nice and tight to ensure optimal performance. Your belt should be changed every 3 to 6 months depending on usage.
You can purchase a wide variety of replacement belts for your Shark vacuum directly from Crucial Vacuum with free shipping and an exclusive 10% coupon for Fixya.com readers, use code: FIXYA10
I hope this was helpful. If you would like further assistance, please feel free to give us a call at 877.750.9239. We have helpful and friendly customer care representatives on the line ready to assist you.
Crucial Vacuum Customer Care