[Plugin: Woocommerce subscriptions] Cancelled sub action hook not firing

For some reason my action hook function is not firing at all. I am almost 100% I have done it correctly, yet it won’t fire when the user clicks ‘Cancel’ under My Account.

My code which is placed in functions.php:

add_action( 'cancelled_subscription', 'cancelsub', 10, 2 );

function cancelsub($user_id, $subscription_key)
{
	$servername = "localhost";
	$username = "root";
	$password = "pass";
	$dbname = "rsrs";

	// Create connection
	$conn = new mysqli($servername, $username, $password, $dbname);
	// Check connection
	if ($conn->connect_error) {
		die("Connection failed: " . $conn->connect_error);
	} 

	$sql = "UPDATE users SET status = 'pending cancellation' WHERE subscription_id = '$subscription_key'";

	if ($conn->query($sql) === TRUE) {
		echo "Record updated successfully";
	} else {
		echo "Error updating record: " . $conn->error;
	}

	$conn->close();
}