Font-awesome: An emoticon looks different on my co

I am trying to add on my webpage the ResearchGate emoticon from academicons which is an extension to font-awesome. Here is what the emoticon should look like:

It works fine when I open my index.html on my computer (user/name/path/to/index.html) but it doesn't work when I open my webpage (www.blabla.bla.bl). Of course, I made really sure to copy (scp) my whole directory (including, images, css, etc..) over the server several times. I made it several times and have now waited 10 hours but the display is still incorrect. The display depends of what web browser I use to watch the webpage. Safari and GoogleChrome display and Firefox displays . Note that other font-awesome icons work fine.

Here is the code in index.html

<li>
  <a href="https://www.researchgate.net/profile/MyName">
     <i class="ai ai-researchgate"></i>
  </a>
</li>

This piece of code is wrapped in ul and in a div of class social-icons

and here is my style.css

.social-icons {
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    /*background: #202020;
    border-top: 1px solid #1A1A1A;*/
    background: #2b2b2b;
    width: 250px;
    z-index: 2;
    height: 45px;
}

.social-icons ul {
    padding: 0;
    margin: 0;
    list-style: none;
}

.social-icons li {
    float: left;
    width: 33%;
    padding: 10px;
    text-align: center;
}

I don't quite understand how font-awesome and academicons work but here is the code in academicons.css

.ai-researchgate:before {
    content: "\e602";
}

Do you have any idea of what might be causing this behaviour?

Edit

    <link rel="stylesheet" href="css/academicons.css">
    <link rel="stylesheet" href="css/bootstrap.css">
    <link rel="stylesheet" href="css/font-awesome.min.css">  
    <link rel="stylesheet" href="css/perfect-scrollbar-0.4.5.min.css">
    <link rel="stylesheet" href="css/magnific-popup.css">
    <link rel="stylesheet" href="css/style.css">
    <link id="theme-style" rel="stylesheet" href="css/styles/default.css">

The links to the font files are on the .css files.

On the font-awesome.css

@font-face{font-family:'FontAwesome';src:url('font/fontawesome-webfont.eot?v=3.2.1');src:url('font/fontawesome-webfont.eot?#iefix&v=3.2.1') format('embedded-opentype'),url('font/fontawesome-webfont.woff?v=3.2.1') format('woff'),url('font/fontawesome-webfont.ttf?v=3.2.1') format('truetype'),url('font/fontawesome-webfont.svg#fontawesomeregular?v=3.2.1') format('svg');font-weight:normal;font-style:normal;}[class^="icon-"],[class*=" icon-"]{font-family:FontAwesome;font-weight:normal;font-style:normal;text-decoration:inherit;-webkit-font-smoothing:antialiased;*margin-right:.3em;}

on the academicons.css

@font-face {
    font-family: 'academicons';
    src:url('fonts/academicons.eot?j69par');
    src:url('fonts/academicons.eot?#iefixj69par') format('embedded-opentype'),
        url('fonts/academicons.woff?j69par') format('woff'),
        url('fonts/academicons.ttf?j69par') format('truetype'),
        url('fonts/academicons.svg?j69par#academicons') format('svg');
    font-weight: normal;
    font-style: normal;
}

The most likely scenario is that your web server is not configured to serve the MIME types used by most modern web fonts. As such, and since you likely cannot reconfigure the server itself, you'll need to add some server directives per project.

For IIS, use the directives from this answer in your web.config:

<staticContent>
   <remove fileExtension=".woff" />
   <remove fileExtension=".eot" />
   <remove fileExtension=".ttf" />
   <remove fileExtension=".svg" />
   <mimeMap fileExtension=".eot" mimeType="application/vnd.ms-fontobject" />
   <mimeMap fileExtension=".ttf" mimeType="application/font-sfnt" />
   <mimeMap fileExtension=".svg" mimeType="image/svg+xml" />
   <mimeMap fileExtension=".woff" mimeType="application/font-woff" />
</staticContent>

The staticContent section will be found within (or need to be added to) the system.web section.

For Apache, add these directives to your .htaccess file:

AddType application/vnd.ms-fontobject    .eot
AddType application/x-font-opentype      .otf
AddType image/svg+xml                    .svg
AddType application/x-font-ttf           .ttf
AddType application/font-woff            .woff