Hi Alexander,
Thanks for writing in! 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.
If you have added your icons manually, you need to change data-x-icon to data-x-icon-b for example, to make it compatible with the latest release.
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!