HTML Dropdown Navbar not displaying

ul {
    position: -webkit-sticky; /*code for safari only*/
    position: sticky;
    top: 0;
    list-style-type: none;
    margin: 0;
    padding: 0;
    overflow: hidden;
    border: 1px solid #3c86a6;
    background-color: #AFD4E5;
    border-radius: 5px;
}

li {
    float: left;
    border-radius: 10px;
}

li a, .dropbtn {
    display: block;
    color: #4a4a4a;
    text-align: center;
    padding: 14px 16px;
    text-decoration: none;
    font-family: 'Oswald', sans-serif;
}

li a:hover:not(.active) {
    background-color: #245164;
    color: #AFD4E5;
    font-family: 'Oswald', sans-serif;
}

li a.active {
    color: aliceblue;
    background-color: #245164;
}

li a:hover, .dropdown:hover .dropbtn {
    background-color: #245164;
    color: #AFD4E5;
}

li.dropdown {
    display: inline-block;
}

.dropdown-content {
    display: none;
    position: absolute;
    background-color: #f9f9f9;
    min-width: 160px;
    box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2);
    z-index: 1;
}

.dropdown-content a {
    color: black;
    padding: 12px 16px;
    text-decoration: none;
    display: block;
    text-align: left;
}

.dropdown-content a:hover {background-color: #f1f1f1;}

.dropdown:hover .dropdown-content {
    display: block;
}

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<body>
  <nav>
    <ul>
      <li><a href="#">Home</a></li>
      <li class="dropdown">
        <a href="#" class="dropbtn">About Maptrix</a>
        <div class="dropdown-content">
          <a href="#">Link 1</a>
          <a href="#">Link 2</a>
          <a href="#">Link 3</a>
        </div>
      </li>
      <li><a href="#">WiseGuide</a></li>
      <li><a href="#">Finance</a></li>
      <li><a href="#">Documentation</a></li>
    </ul>
  </nav>
</body>
</html>