Hi There @shughesd ,
Thanks for writing in! Upon checking your site, I see that you have added those icons through your Topbar using HTML. As of Font Awesome version 5.x, they split icons into multiple fonts. This can be fixed by changing instances of the data-x-icon attribute to one of the following:
data-x-icon-b for social icons.
data-x-icon-o for outline icons.
data-x-icon-s for solid icons.
The original attribute data-x-icon will still work for solid icons as a fallback but we’ve updated everything for consistency.
After making the changes, If you’re using a caching plugin, make sure to purge your server cache after updating. Please refer to the following article on how to clear full cache (https://www.wpbeginner.com/beginners-guide/how-to-clear-your-cache-in-wordpress/).
Hope that helps.
Thanks!