Only "fas fa" icons appear

[lovemeblender]

I'm on Rails 7.0.3 and Ruby 3.2.0, using font-awesome-sass 6.4.2. I can only see icons which are "fas fa" e.g. fas fa-envelope but not for example fab fa-instagram.

In my application.scss, I've got:

@import "font-awesome";
$fa-font-path: "@fortawesome/fontawesome-free/webfonts";

I recently upgraded Rails and Ruby and font-awesome-sass so not sure if the issue sits with font-awesome-sass but checking anyway. This used to work before the upgrade.