HTML/CSS导航栏下拉菜单不以列表格式显示

<nav class="navbar">
  <ul class="nav-list">
    <li class="nav-item"><a href="#">Home</a></li>
    <li class="nav-item dropdown">
      <a href="#" class="dropbtn">Services</a>
      <div class="dropdown-content">
        <a href="#">Service 1</a>
        <a href="#">Service 2</a>
        <a href="#">Service 3</a>
      </div>
    </li>
    <li class="nav-item"><a href="#">About</a></li>
  </ul>
</nav>

.navbar {
  background-color: #333;
}

.nav-list {
  list-style-type: none;
  margin: 0;
  padding: 0;
  display: flex;
}

.nav-item {
  position: relative;
}

.dropbtn {
  color: white;
  padding: 14px 20px;
  text-decoration: none;
  display: 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;
}

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