I had the same problem. The cover has a white, plastic wedge shaped piece that presses down on the white rod to allow the motor to engage. The problem is that this wedge is not being forced down enough.
Solution: Remove the white wedge and insert a 1/2 inch piece of hard plastic and then reinsert the wedge. The piece of plastic you insert should be enough to press the wedge down enough to in turn press the white rod into the base to allow the motor to engage.
Good luck
Gary
January 2008