Icons Invisible Since WordPress Update

I am having the same issue with Infinity Pro theme. The icons do not show up no matter what. They are present in the source code, but are not displaying, even though there is no CSS causing them to be invisible.

I reached out to the StudioPress forum and was made of aware of the fact that there has been a huge change with Simple Social Icons. That may be the source of your problem.

See this link:
https://www.studiopress.com/simple-social-icons-2-0/