Hi there,
Thanks for the callout. I’ve been swamped and thus haven’t been updating the fallback version regularly. Should be all set with version 1.6.0 now.
That said, I do want to clarify that the request to the CDN version of Font Awesome is protocol agnostic. Specifically, this is what it looks like:
$this->stylesheet_url = '//cdn.jsdelivr.net/fontawesome/' . $version . '/css/font-awesome' . $this->get_min_suffix() . '.css';
So protocol (http vs https) probably isn’t the issue unless you’ve set up some specific headers/settings for your site.