No style selected

Installing FontAwesome Pro

This site is barely updated anymore :/ 
@import url('https://site-assets.fontawesome.com/releases/v6.6.0/css/all.css');
@import url('https://site-assets.fontawesome.com/releases/v6.6.0/css/sharp-solid.css');
@import url('https://site-assets.fontawesome.com/releases/v6.6.0/css/sharp-thin.css');
@import url('https://site-assets.fontawesome.com/releases/v6.6.0/css/sharp-duotone-solid.css');
@import url('https://site-assets.fontawesome.com/releases/v6.6.0/css/sharp-regular.css');
@import url('https://site-assets.fontawesome.com/releases/v6.6.0/css/sharp-light.css');

See the example: codepen.io/GavinGoGaming/eYLGqWx

Empty

ID: empty
Categories: a, b, c

Use in code

HTML: 
<i class="fa-empty fa-empty"></i>
React: 
<i class="fa-empty fa-empty"></i>
Vue: 
<i class="fa-empty fa-empty"></i>