Wheels not turning

I have a 85mhp17 and a few months ago I replaced the plastic tube with one I bought from you. It has been working great. However another problem has surfaced. The motor is operating as I can hear it however the white plastic wheels that the tube encircles are not turning. If I apply any pressure to the clear plastic housing the pump makes a louder whining noise. Any ideas as to what this can be? Thanks, Bryan