The button is fine. There is an element just above the additional links section that is causing the problem by having the bottom of it overlap the additional links section. it’s got a large transparent section at the bottom which is why you can’t see it. It’s an embed element with the embed url:
If you z-index that back or z-index the links section forward and that should fix the problem.
As a personal question, did you use the edge suite to build this site. There’s a whole lot of stuff going on and I was just wondering if that’s the edge code output.