If you found the spring that lies at the bottom when you look into the little access hole, then you should also see the wheel. It may be covered in dust. Use the screwdriver and slide it along the spring till it hits the wheel then you know where it is - it is quite thin. It has points on the ends and if you lever a screwdriver against the tip and push down against the hole it should turn. They can be stiff if not moved for a while. As the wheel turns, the point passes the spring and it sits in the next groove in the wheel.....but could not make it work.
Found the spring all right but could not make it move and certainly not to "click"....any suggestions????