I do not know what is your problem, but mine was: when the customer chose banking ticket as payment method, WooCommerce changed the order status to on-hold, and afterwards the user received ‘processing order’ email notification. That is how WooCommerce works by default, so I had to disable the trigger:
/**
* Disable action that sends e-mail to customer warning that his/her order is processing,
* as this is not true, because when the status changes from pending to on-hold,
* the order is not processing yet.
*
* @return void
*/
function woocommerce_email_sending($email_class){
remove_action('woocommerce_order_status_pending_to_on-hold_notification', array($email_class->emails['WC_Email_Customer_Processing_Order'], 'trigger'));
add_action('woocommerce_order_status_on-hold_to_processing_notification', array($email_class->emails['WC_Email_Customer_Processing_Order'], 'trigger'));
}
add_action('woocommerce_email', 'woocommerce_email_sending');
