This simple tip is for those of you who have legacy Blocs 3.x documents that use FontAwesome icons.
Blocs 4 does its best to auto-convert your old FontAwesome icons to the new version that Blocs 4 uses. However, this conversion does not extend to Code Widgets, so you will need to update those manually. Here is a table that can help you in that conversion:
In many cases, you simply need to change the old “fa” code to “fab”.
For large sites you may not notice where there is a problem, and there is no easy way to track them down other than just go through every page in your site, including your menus, and check to see what is missing. In my own Blocs 3.5.5 documents, I have found icons missing in my mega-menu, and in every case I am using a Code Widget. Fixing the code inside the Code Widgets will cause the icon to display again.