I am trying to use unicodes in css for FA5, but it is not always working. The icons work if I use the html markup.
Code below, and also a fiddle. You will see the first works, using a justify icon, but the second accessible icon does not work.
https://jsfiddle.net/s6qkcnyb/
<html>
<head>
<title></title>
<link rel="stylesheet" href="https://use.fontawesome.com/releases/v5.8.1/css/all.css">
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<style>
.justify::after {font-family: "Font Awesome 5 Free"; content: "\f039"; white-space:pre; font-weight: 900; }
.accessible::after {font-family: "Font Awesome 5 Free"; content: "\f368"; white-space:pre; font-weight: 900; }
</style>
</head>
<body>
<div>This is using html : <i class="fas fa-align-justify"></i></div>
<div class='justify'>This is using css : </div>
<hr>
<div>This is using html : <i class="fab fa-accessible-icon"></i></div>
<div class='accessible'>This is using css : </div>
</body>
</html>