By not working, I am assuming you mean it is still showing the default anim? Usually a bug like this is caused by the set default animation overruling the button click logic elsewhere on the event sheet. Do you have any other conditions for setting the default animation that might be constantly true, so if you clicked the button it would still switch back to the default animation?
mmh..yeah, the default animation is working.
An other condition is this, but I don't think that this is the problem.