Show/Hide footer on scroll

Question

Im trying to make a footer fully showing in the bottom once I scroll.

https://teste.contahl.com/

It is working on desktop, but not in mobile, can someone help me with?

Tkx

CSS---

footer{
    position:fixed;
    bottom:0;
    height: 10vh;
    width: 100vw;
    transition: bottom 0.2s ease-in-out;
}

JS---

var prevScrollpos = window.pageYOffset;
window.onscroll = function() {
var currentScrollPos = window.pageYOffset;
  if (prevScrollpos > currentScrollPos) {
    document.getElementById("footer").style.bottom = "0";
  } else {
    document.getElementById("footer").style.bottom = "-5vh";
  }
  prevScrollpos = currentScrollPos;
}