If you find that the tool is not picking up, it may just need to be opened and cleaned. Open the cover and make sure it is free from debris or foreign objects. Also remove any hair or thread build up around the little brush roll. It is normal for the drive belt which looks like an elastic band to feel loose or slack, but if the belt has snapped then the nozzle will need to be replaced. The air current from the vacuum cleaner is used to make the brush rotate. If the suction power is poor, then the brushes won’t spin. Check that the hose is not clogged, empty the dust box and clean all of the filters to ensure a strong suction power which in turn will make the nozzle work better. So look at the trouble shooting guide for your particular cleaner which is available on this website. Depending on what model you have the way in which the cover is removed to get the tool apart may vary. The sides may prize apart, there may be a locking ring or a locking catch to release the cover. Some have buttons to press on the stem after 2 screws have been removed. Refer to the images for further help:

Tool open for cleaning, note the white drive wheel should be free from debris