However if one is stuck with the problem and it is early enough in the disease, you can force the blades to move, for a while/few sessions at least, by assigning the Depth of Field preview function to the Fn button. After turning the camera back on, press Fn - and then you should see the blades move for a while. I found that after turning the camera back on and off I'd have to fire off DoF preview again.
One of my students got her camera back on Monday. It's being sent back for repair again as it either wasn't fixed or... The replacement lens unit is faulty. I tested the camera last nite and it's defective.