Yes I tried to view your website and error is there. You can contact your hosting provider as we have nothing to do with the wp-config at all. Once you check your files through FTP or cPanel you can make changes there and once done let us know too ?
Have you made sure that the font is actually installed ? To show in general settings it may needed some coding skills. But first try to see by writing CSS if your font is working fine.
Like this is a code
body p{ font-family: “your new font family name”;}
And see if that font shows up or not etc ? You can use proper element class to test font.
You can always get latest version from your specular theme’s downloaded package. It resides inside the inlcuded_plugins folder and no need to have any key for that.
