Why is my Kenmore with Micron filter not picking up anything?

I have a Kenmore Quick clean w/Micron Filtration( Upright model) that one day stopped picking up anything,It's less than a year and used to pick up really awesome.The attachment hose picks up still but when you try to vacuum regularly it wont pick up anything and my allergy's are killing me from all the cat and dog hair on the carpet...HELP