For everyone having issues with mobile social icons not showing up give my suggestion a try from this post:
The theme is filtering what it does based on screen size (this is what responsive means) because of that viewing this theme on smaller screen sizes may result in the social icons not showing up, or only their backgrounds showing up. The reason is because it is trying to find an icon image file that doesn’t currently exist. If you comment out a chunk of code from the original style.css file it will force the theme to use the icon image file it uses on the larger screen sizes.
This worked for me, and hopefully it will work for you as well.
If you do try this, make sure you backup your style.css file just in case you want to undo the changes you made.
Re: Social Buttons