A common issue with Kirby shampooer belts is the belts tend to get stretched out when you are no longer using your shampooer.   Then when you go to shampoo your floors again you notice that the brushroll is not spinning very good.   

No worries it is an easy solution.  It just needs a new belt.  Shipping costs have got so expensive that we now have to sell these in a 5 pack but this should be enough to last you several years.