Custom deny email subject not working

I am using the following in my functions.php but it simply isn’t working:

function my_deny_subject( $subject ) {
	$subject = 'My website name – Your account is denied';
	return $subject;
}
add_filter( 'new_user_approve_deny_user_subject ', 'my_deny_subject' );

What am I doing wrong?

https://www.ads-software.com/plugins/new-user-approve/