the 'Mechanical Jeb - Pod version - Decoupler' part wont attach.

i am trying to make a craft with the ball shaped mech jeb pod, but it looked weird, so i went to use the pod holder decoupler, but one of the green attach points wont work, so i either cant attach it to the pod, or i cant attach anything underneath it. ive tried flipping it around and a bunch of other things, but it wont work. anyone know whats wrong?