I got it working by adding this:
// Update Nav On Scroll
$(window).scroll(function() {
var scrollDistance = $(window).scrollTop();
$('.page-section').each(function(i) {
if ($(this).position().top <= scrollDistance + 104) {
$('.nav-item.active').removeClass('active');
$('.nav-item').eq(i).addClass('active');
}
});
}).scroll();