Can’t display custom menu using name?

wp_nav_menu() does not have a name argument. Instead, you should use theme_location.

With register_nav_menus(), you indicate that you have two locations in your theme where you can display a menu. The user can then create multiple menus, and assign them to these locations. This is why we have the indirection via theme_location. If you know the ID, slug or name of the menu you want to use, you can use the menu argument of wp_nav_menu().