Why is my hamburger menu not shown? [closed]

The hamburger is shown with ionicons as an after element. You have conflicting CSS in your theme.

This (specifically, the content: " ";) CSS:

.entry:before, .entry-content:before, .nav-primary:before, .site-container:before, .site-header:before, .site-inner:before, .wrap:before {
    content: " ";
    display: table;
}

is overwriting the hamburger menu’s CSS

@media only screen and (max-width: 800px){
  .menu-toggle:before, .menu-toggle.activated:before {
    color: #1e1e1e;
    content: "\f130";
    display: inline-block;
    font: normal 20px/1 'ionicons';
    margin: 0 auto;
    padding-right: 10px;
    text-rendering: auto;
    -webkit-transform: translate(0,0);
    -ms-transform: translate(0,0);
    transform: translate(0,0);
    vertical-align: middle;
  }
}

Here’s a devtools screenshot: https://i.imgur.com/M0zOPb8.png