Some FontAwesome icons not displaying

Hi there,

I use Elementor as my page builder. Recently I noticed that some font awesome icons are not displaying properly anymore. Take a look at https://masterplanacademe.com/contact-us/

On the right, the second icon above the email address should be envelope-o and the one below should be skype

Likewise the buttons should be paper-plane-o

Any idea what could be causing this?

Thanks,
Thomas