Add attributes to print order

Hi guys
Fails to add attributes when order print.
Attribute is “author”

i use this code from FAQ

function example_custom_order_fields( $fields, $order ) {
    $new_fields = array();

    if( get_post_meta( $order->id, 'author', true ) ) {
        $new_fields['author'] = array( 
            'label' => 'VAT',
            'value' => get_post_meta( $order->id, 'author', true )
        );
    }

    if( get_post_meta( $order->id, 'author', true ) ) {
        $new_fields['author'] = array( 
            'label' => 'Author',
            'value' => get_post_meta( $order->id, 'author', true )
        );
    }

    return array_merge( $fields, $new_fields );
}
add_filter( 'wcdn_order_info_fields', 'example_custom_order_fields', 10, 2 );