Why isn't my toggler button displaying the li?

https://codepen.io/CeciPeque/pen/gyQOMV when I click the hamburguer icon the background it’s set to pink but the list items are not there, why is that?

but I did added look

Did you add popper?

https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.15.0/popper.min.js

Bootstrap 4 is using Jquery-3.3.1.

You added the CSS file instead of the JS file.

yes indeed I added the css and not the js file that was the problem, thanks!