UI Button Element Can Not Be Front of Images although hierarchy is right

Hi, I have tried to make my Button be front of my images/gui but failed, although hierarchy has ben set for Button to Bottom but can’t solved.

Any Idea ?

The z axis should always be at 0, I was just wondering if you had one that was greater or less than the other. Set them all back to 0 and try to play around with the hierarchy order of the elements.