element animated but not visible

[sheriff-rango]

Hi
I would like to make slide up animation effect and but the elements aren't visible when first refreshing.
Only navigate from other page, the animations works properly.

This is what I deployed. https://humans-frontend.herokuapp.com/
As you can see from the url, there is no content on home page. But if I navigate to other page and return by click Home menu item, all contents are visible.

I am not sure why this happens.
Please help me!