Separators not showing

That’s normal: in WordPress, admin menu separators just create some additional blank space between the menus that they separate. That’s how it works for the default separators added by the WP core, and the separators you can create in AME are the same.

To make the separators visible, you would need to apply some custom CSS to them. Here’s a very basic example:

#adminmenu#adminmenu li.wp-menu-separator {
    height: 5px;
    margin: 3px 0;
    background-color: white;
}

There are various plugins that can add custom CSS to the admin dashboard. For example (not tested):
https://wordpress.org/plugins/admin-css-mu/