I can't get chin bone to act as a driver for the shape key mouth open

I am following a tutorial here: https://www.youtube.com/watch?v=Wk9OnCyVyTo I think I followed the steps correctly, but the chin bone doesn’t move the mouth on any axis. Can someone tell me what I did wrong?

Blend file: http://www.pasteall.org/blend/37260

I didn’t download the blend but I can see that you have disabled the influence of the ‘mouth open’ shape key. Just to the right of the text ‘mouth open’ there’s a little eyeball icon, it’s greyed out, meaning the shapekey will not be evaluated, click the eyeball.

He does say to right click on the 0.000. I should have paid closer attention. That fixed it. I wasted at least an hour trying to figure out what I did wrong. Thanks for responding. Very much appreciated.