How can I fix my Dyson Slimline?

My Dyson is 1 yr. old. I noticed recently that my Dyson is not picking up dirt right when used as an upright. The dirt does not go up through the cyclone or into the bagless container. It gets stuck in the U-shaped flexible hose. Using the above the floor wand works fine. I cleaned out the U shaped flexible hose between the sweeper and the Hepa filter part, but it still does not send the dirt where it should go. What's wrong?