simple-custom-css.php is not showing up

Here:
wp-admin/themes.php?page=simple-custom-css.php
I have inserted this code:

<?php

/* NOT WORKING: hide the field "ship to a different address?" ="Spedizione a un indirizzo differente?" */

.woocommerce-page form .form-row#ship-to-different-address {
display: none;
}

/* to show biggest products list then here http://www.spesagodina.it/screenshots/Screenshot_2016-02-05-16-19-04.png */

@media
only screen and (max-width: 767px){
   html .woocommerce .products li.product, html .woocommerce-page .products li.product{width: 48%; }
}

/* Enter Your Custom CSS Here */
#header .nav > .main-menu > ul.menu > li img {
margin-bottom: 0 !important;
}

/* gallery with 3 columns */
.gallery-columns-3 .gallery-item {
float: left;
}

/* change pragraph font size */
.entry-content-post{
font-size: 18px;
line-height: 18px;
}

/* change pragraph link size */
.entry-content-post a{
font-size: 18px;
line-height: 18px;
}

/* hide the category filter in the top search form */
#header .v3 .header_search_categories div.select_category {
    display: none;
}
#header .v3 .header_search_categories .search_content {
    width: 100%;
}
/* hide the category filter in the top search form also in the checkout page */
#header .v3 .header_search_categories div.select_category {
display: none !important;
}

You can check it here too: http://spesagodina.it/web/
Why? Please help! I was reading the FAQ, but it is no all so much clear to me..

https://ww.wp.xz.cn/plugins/simple-custom-css/