Hello, @maspegren.
Thank you for your question – we are using the fourth version of Font Awesome in our plugin, because in the fifth version they moved a lot of icons to a paid PRO version. I recommend you to backup styles for Font Awesome on your website, so you can use all necessary icons without any issues.
That unfortunately isn’t an option for me since the FontAwesome version is coming from the theme and used in multiple other places. I just overwrote the specific icon I was having issues with. Not ideal, but works for the mean time. Thanks for your response.