Exact steps for others to reproduce the error
If after animating a bone, you rename it, when you play the animation again it doesn't move. You have to save and open the file again, or change the name of the bone to the previous one.
Open a new file, create a bone, animate it with two keyframes, and play the animation. Change the name of the bone, and play the animation again. It won't move now. Save, reopen, and it will move.
I don't include a blend file because saving fixes this