Navbar icon not showing in some browsres
<p>I am working on a responsive webpage. I am using a custom navbar, as follows;</p>

<p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
<div class="snippet-code">
<pre class="snippet-code-js lang-js prettyprint-override"><code>      function myFunction() {
        var x = document.getElementById("myTopnav");
        if (x.className === "topnav") {
          x.className += " responsive";
        } else {
          x.className = "topnav";
        }
      }</code></pre>
<pre class="snippet-code-css lang-css prettyprint-override"><code>/* Remove margins and padding from the list, and add a black background color */

ul.topnav {
  list-style-type: none;
  margin: 10;
  padding: 10;
  overflow: hidden;
}
/* Float the list items side by side */

ul.topnav li {
  float: left;
  margin: 10;
  padding: 10;
}
/* Style the links inside the list items */

ul.topnav li a {
  display: inline-block;
  color: #f2f2f2;
  text-align: center;
  padding: 14px 16px;
  text-decoration: none;
  transition: 0.3s;
  font-size: 40px;
}
/* Change background color of links on hover */

/* ul.topnav li a:hover {background-color: #fff;}
    
    /* Hide the list item that contains the link that should open and close the topnav on small screens */

ul.topnav li.icon {
  display: none;
}
/* When the screen is less than 680 pixels wide, hide all list items, except for the first one ("Home"). Show the list item that contains the link to open and close the topnav (li.icon) */

@media screen and (max-width: 680px) {
  ul.topnav li:not(:first-child) {
    display: none;
  }
  ul.topnav li.icon {
    float: right;
    display: inline-block;
  }
}
/* The "responsive" class is added to the topnav with JavaScript when the user clicks on the icon. This class makes the topnav look good on small screens */

@media screen and (max-width: 680px) {
  ul.topnav.responsive {
    position: relative;
  }
  ul.topnav.responsive li.icon {
    position: absolute;
    right: 0;
    top: 0;
  }
  ul.topnav.responsive li {
    float: none;
    display: inline;
  }
  ul.topnav.responsive li a {
    display: block;
    text-align: left;
  }</code></pre>
<pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;ul class="topnav" id="myTopnav"&gt;
  &lt;li&gt;
    &lt;a href="#news"&gt;
      &lt;img class="img-responsive" width="60px" src="imagenes/botones/logo_hera.png" /&gt;
    &lt;/a&gt;
  &lt;/li&gt;
  &lt;li&gt;
    &lt;a href="#news"&gt;
      &lt;img class="img-responsive" width="180px" src="imagenes/botones/doctores_boton.png" /&gt;
    &lt;/a&gt;
  &lt;/li&gt;
  &lt;li&gt;
    &lt;a href="#news"&gt;
      &lt;img class="img-responsive" width="180px" src="imagenes/botones/hospitales_boton.png" /&gt;
    &lt;/a&gt;
  &lt;/li&gt;
  &lt;li&gt;
    &lt;a href="#news"&gt;
      &lt;img class="img-responsive" width="180px" src="imagenes/botones/farmacias_boton.png" /&gt;
    &lt;/a&gt;
  &lt;/li&gt;
  &lt;li&gt;
    &lt;a href="#news"&gt;
      &lt;img class="img-responsive" width="180px" src="imagenes/botones/laboratorios_boton.png" /&gt;
    &lt;/a&gt;
  &lt;/li&gt;

  &lt;li class="icon"&gt;
    &lt;a href="javascript:void(0);" onclick="myFunction()"&gt;&amp;#9776;&lt;/a&gt;
  &lt;/li&gt;
&lt;/ul&gt;</code></pre>
</div>
</div>
</p>

<p>On my PC and my iPhone, I can see the navbar icon as I want:</p>

<p>iPhone Screenshot:
<a href="https://i.stack.imgur.com/NHwad.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/NHwad.jpg" alt="enter image description here"></a></p>

<p>But on my Android device it looks as follows:</p>

<p><a href="https://i.stack.imgur.com/xcVIS.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/xcVIS.png" alt="enter image description here"></a></p>

<p>There is no navbar icon visible.</p>

<p>What is wrong at my code?</p>

<p>EDIT:</p>

<p>I know the toggle icon is there, but not visible. It works when touched</p>