Font Awesome only displaying brand icons

I'm trying to use Font Awesome icons on my website, but any icon other than the 'brand' icons (fab) just display as boxes.

This is what appears:

https://imgur.com/a/HIukIAr

The second icon should have been a camera icon, but it appears as a box because it is not a 'brand' icon.

Here's how I've set up Font Awesome (I followed the instructions on their website). I have this in my <header> tag (I've hidden part of the URL for security purposes):

<script src="https://kit.fontawesome.com/--------.js"></script>

When I used the Github brand icon, this was the code I used:

<span style="padding-bottom: 30px;"><i class="fab fa-github fa-2x"></i></span>

And to use the camera icon, this is the code I used:

<span style="padding-bottom: 30px;"><i class="fas fa-camera fa-2x"></i></span>

It should display a camera icon on the right (see image), but it just displays an empty box. I have tried several solid icons (fas) but they all display as boxes. Only the icons listed under the brand category (fab) seem to work.