I recently had to recable a hybrid bike as a result of a handlebar change. I cut the shifter cable for the rear derailleur, clicked it to the position where I could push the cable out, inserted a new cable, clicked it all the way out to the #8 position, bolted the free end of the cable to the rear derailleur, and found that it doesn't work. That is, the mechanism goes through all seven clicks, both up and down (it's an 8-speed shifter) but it doesn't pull any cable. Removing the dust cover and looking at the ratcheting mechanism as it operates seems to indicate that it's working as it should. It was functioning perfectly before I recabled it. Shifter and cable are off the bike now, but I can't get the shifter to pull any cable no matter what I do.
What gives? It's as if the stop at the shifter end of the cable is not engaging in the right place--otherwise I can't see why it's not moving when the shifter moves. As far as I can tell, though, it's pulled into the shifter as it should be. But since it's invisible once it's pulled in to where it seats, I can't say for sure that it's in the right place.

Edit--figured it out. I'm an idiot--forgot to click to 8 before inserting the cable. I'll go back to C & V, where I belong.

Are you sure that you inserted the cable when the shifter was in the correct position.

It will go in when the shifter is at either end of the click / gear range, but only one is correct, and will allow it to shift.

If you shine a light into the shifter hole, you will be able to see where the end of the cable sits when the position is correct. insert it fully, then hold the cable tight, use the shifter, and you will feel it pull the cable in.