fullPage.js by default hides the scrollbar making it impossible for events relying on the scroll event to work as expected.

To tix this all you have to do is enable the scrollbar on fullPage.js by using the option scrollBar:true. This way fullPage.js snap effect will still work and you'll be able to enjoy from Wow.js animations.

If you still prefer to keep the scrollbar hidden, as the animation will be a bit smoother, you can use fullPage.js callbacks such as onLeave or afterLoad to add the necessary classes Wow.js require to trigger the animation.

Here's an example:

afterLoad: function(origin, destination, direction){
    $(destination.item).find('.to-animate').addClass('animated fadeInLeftBig');
},

Or if you do not use jQuery:

afterLoad: function(origin, destination, direction){
     destination.item.querySelectorAll('.to-animate').forEach(function(item){
          item.classList.add('animated', 'fadeInLeftBig');
     });
},

You can find more about this topic on the Github issues forum as well as on Stackoverflow.