Send an email notification when order status change from pending to cancelled

Question

In previous versions of Woocommerce, an email notification was sent automatically when an order was changed from pending status to cancelled status (In my case, this happens

Answer 1

The good new: Using woocommerce_order_status_pending_to_cancelled action hook with a custom function hook in it, solve your problem definitively:

add_action('woocommerce_order_status_pending_to_cancelled', 'cancelled_send_an_email_notification', 10, 2 );
function cancelled_send_an_email_notification( $order_id, $order ){
    // Getting all WC_emails objects
    $email_notifications = WC()->mailer()->get_emails();

    // Sending the email
    $email_notifications['WC_Email_Cancelled_Order']->trigger( $order_id );
}

Code goes in function.php file of your active child theme (or theme) or also in any plugin file.

Tested and perfectly works in WooCommerce 3+ (and 3.1+)