From what I can see, you have an invisible div of some sort on a z-index on top the div that contains these links, and it's interfering with your ability to click them. The .backtotop property has a z-index of 100, yet it's bounding box is enormous and it's right aligned? If you added a background color to it, you'd see it's literally physically covering everything in your footer, making any clicking to things below it impossible.
If I delete the node for .backtotop entirely, the links all work. You'll have to find some other way to position your back to top button.
You might consider
replacing it entirely.