Using a different icon font

Hello WPMU team,

We are having problems with using a different icon font than the default upfront one. The problem is that when I upload file (in Upfront -> Builder -> Theme Settings -> Theme Icon Fonts) , it doesn't get recognised as a icon font set. Also, I can not delete it as I get an error "file could not be found". I have also tried to apply our icon set by replacing the upfront fonts with ours ( files). Still, the icons are not recognised. Can you tell us what is wrong with our font files and how should we generate the right ones which can be used in the Builder?