Hi, Els! It looks like your theme’s stylesheet is overriding the plugin’s new font. To fix this, you can edit your stylesheet via Appearance → Editor or with an FTP application, then change this code (line 1984):
.nav-primary .simple-social-icons ul li a {
border: none !important;
box-sizing: content-box;
display: inline-block;
font-family: 'fontello';
font-size: 14px !important;
font-style: normal !important;
font-variant: normal !important;
font-weight: normal !important;
line-height: 1em;
padding: 2px !important;
speak: none;
text-align: center;
text-decoration: none !important;
text-transform: none !important;
width: 1em;
-moz-osx-font-smoothing: grayscale;
-moz-box-sizing: content-box;
-webkit-box-sizing: content-box;
-webkit-font-smoothing: antialiased;
}
To look like this (changed ‘fontello’ to ‘ssi-icomoon’, fifth line down):
.nav-primary .simple-social-icons ul li a {
border: none !important;
box-sizing: content-box;
display: inline-block;
font-family: 'ssi-icomoon';
font-size: 14px !important;
font-style: normal !important;
font-variant: normal !important;
font-weight: normal !important;
line-height: 1em;
padding: 2px !important;
speak: none;
text-align: center;
text-decoration: none !important;
text-transform: none !important;
width: 1em;
-moz-osx-font-smoothing: grayscale;
-moz-box-sizing: content-box;
-webkit-box-sizing: content-box;
-webkit-font-smoothing: antialiased;
}
After clearing WordPress caching plugins and your browser cache, you should find that solves things for you. (I tested this in Chrome’s developer tools and your icons are restored for me after that edit: https://d.pr/i/16n7L )