atmadja

Edit : I found the solution.

Here is the code I use :

// Add a new custom column to admin order list
add_filter( 'manage_edit-shop_order_columns', 'admin_orders_list_add_column', 10, 1 );
function admin_orders_list_add_column( $columns ){
    $columns['custom_column'] = __( 'New Column', 'woocommerce' );

    return $columns;
}

// The data of the new custom column in admin order list
add_action( 'manage_shop_order_posts_custom_column' , 'admin_orders_list_column_content', 10, 2 );
function admin_orders_list_column_content( $column, $post_id ){
    global $the_order;

    if( 'custom_column' === $column ){
        $count = 0;

        // Loop through order items
        foreach( $the_order->get_items() as $item_id => $item ) {
        	$allmeta = $item->get_meta_data();
        	$somemeta = $item->get_meta( 'Plat', true );

            // Display order meta data
        	//print_r($allmeta);
        	print_r($somemeta);

            $count++;
        }
    }
}

If someone need, the meta key (in my case “Plat”) can be found here :

Hope this post will help you.
Thanks community.

Ok, so I found the problem.
It must be a problem with my browser cache or someting like that because with an other browser i can now publish pages.
And after a simple restart of my original chrome browser, it also works know.
Hope it will help someone in the same case.