Kirby 2001 Limited Edition

Question

Vacuum is not picking up very much debris from the carpet and the little that it is is being blown back out through the sides. It is doing completely the opposite to what it should - blowing air out instead of sucking it up. (I have checked that the bag is not full)/ I had someone looking after my house while I was away but cannot contact this person. I feel she may have done something quite simple for this problem to have occurred and I hope you can help me. It may take just the flick of a switch, although I've tried just about everything.
Thank you for your time.