Fontello Social Icons Not Displaying

I set-up three social icons from Fontello in the header of a website I launched a few weeks ago. I needed some help from here getting them set-up (https://kriesi.at/support/topic/using-different-social-media-icons-adjusting-spacingsize/), but eventually got everything sorted out. I just noticed today in Frirefox and Chrome the icons aren’t displaying. If someone could have a look and help figure out why that is happening, that would be great. Thanks!