下拉导航栏不出现

Question

让我抓狂了几个小时的问题是，响应模式下的下拉菜单（当您将页面大小调整为600px时）无法正常工作。请帮助我：演示https://nav5.netlify.com/ github文件：https://github.com/odito/nav5

我尝试解决此问题。但是看来我有问题。

*{
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

nav {
    display: flex;
    justify-content: space-between;
    background: #333;
}

.logoBasic {
    padding:5px;
}

.logo {
    width: 40px;
    margin-left: 10px;
}

.logo img {
    width:40px;
    margin-top: 2px;
}

.menu-area {
    background: #333;
    align-self: center;
}

a {
    color: inherit;
    text-decoration: none;
}

.menu-area ul li ul {
    -moz-transition: all 300ms ease-in-out 300ms;
    transition:all 300ms ease-in-out 300ms;
     -moz-transform: rotateX(-90deg);
    transform: rotateX(-90deg);
     -moz-transform-origin: 0% 0%;
    transform-origin: 0% 0%;
    backface-visibility: hidden;
    position: absolute;
    padding-top:10px;
    text-align:left;
}

.menu-area ul li:hover ul {
    -moz-transition: all 300ms ease-in-out 0ms;
      transition:all 300ms ease-in-out 0ms;
     -moz-transform: rotateX(0deg);
      transform: rotateX(0deg);
}

.menu-area ul {
    padding:0px;
    color:rgb(214, 207, 207);
    background: #333;
    perspective: 300px;
    transform-style: preserve-3d;
    display: inline-block;
    list-style: none;
    position: relative;
    margin-right: 20px;
    width:100%;
    height:auto;
}
.open {
    height:auto;
}

.menu-area ul:after {
    content: '';
    clear: both;
    display: block;
}

.menu-area ul li {
    float: left;
    transform-style: preserve-3d;
    perspective: 300px;
}


.menu-area ul li:last-of-type {
    border-right: none;
}

.menu-area ul li:hover {
//background: #fff;
}

.menu-area ul li:hover >a {
    color: #fff;
}

.menu-area ul li a {
    display: block;
    padding: 5px 25px;
    text-transform: uppercase;
}

.menu-area ul li ul li {
    float: none;
    position: relative;
    border:none;
}

.menu-area ul li ul li a {
    padding: 10px 30px;
}

.logoBtn .bar {
    width:30px;
    height: 3px;
    background: rgb(211, 208, 208);
    margin: 4px;
}

.logoBtn .btn {
    border: 1px solid red;
    display: none;
}

.fa-caret-down {
    margin-left:5px;
}

@media screen and (max-width:575px) {
    nav {
        display: block;
    }

    .menu-area ul {
        display: block;
        margin-right: 0px;
        width: 100%;
        height:0;
        overflow: hidden;
        transition: all 1s ease;
    }

    .menu-area ul.open {
        height: 198px;
    }

    .menu-area ul li {
        float: none;
        transform-style: preserve-3d;
        perspective: 0;
        border-right: none;
        position: relative ;
    }

    .menu-area ul li  ul {
        position: absolute;
        padding-top:0px;
        background: rgb(134, 83, 83);
        border-top:0;
        margin:0;
        height: auto;
    }

    .menu-area ul li:hover ul {
        display: block;
    }

    .menu-area ul li ul li {
        display: block;
        width:100%;
        padding-top:0px;
        background: rgb(134, 83, 83);
        border-top:0;
        margin:0;
    }

    .menu-area ul li a {
        padding: 15px;
    }

    .logoBtn .logo {
        margin-left: 10px;
    }

    .logoBtn {
        display: flex;
        justify-content: space-between;
        align-items: center;
        border-bottom:1px solid rgb(158, 156, 156);
    }

    .logoBtn .btn {
        border: 1px solid rgb(187, 183, 183);
        display: block;
        cursor: pointer;
        margin-right: 20px;
    }
}