Disappearing Social Media Buttons

I just downloaded this theme for my new website and I love it. I entered the links for my social sites in theme customization, and the buttons show up as long as I’m in the theme customization area. As soon as I go to view the site, however, the buttons disappear. The links are present. I can hover over the spot where the button should be and it indicates there is a link there, but the button is black on a black background.

In the header social options section, if I try to change either the social link color from the default or the social link hover color from default to any other color, I get a little message that says invalid value and prevents me from saving.