Magento 2 email_order_set_template_vars_before observer triggers only when I resend email in the admin

Question

I created a new template var using email_order_set_template_vars_before observer and it works when I send email new order through the Magento admin. But it does not trigger when new order is placed. Here is my code.

events.xml

<?xml version="1.0"?>
<!--
/**
 * Copyright © 2015 Magento. All rights reserved.
 * See COPYING.txt for license details.
 */
-->
<config xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="urn:magento:framework:Event/etc/events.xsd">

    <event name="email_order_set_template_vars_before">
        <!-- <observer name="shipperhq_save_email_variables" disabled="true"/> -->
        <observer name="cd_shipperhq_save_email_variables" instance="Foobar\ShipperHQDeliveryDate\Observer\SaveEmailVariables"/>
    </event>

</config>

SaveEmailVariables.php

namespace Foobar\ShipperHQDeliveryDate\Observer;
use Magento\Framework\Event\ObserverInterface;

class SaveEmailVariables implements ObserverInterface
{
    private $carrierGroupHelper;
    public function __construct(\ShipperHQ\Shipper\Helper\CarrierGroup $carrierGroupHelper) {
        $this->carrierGroupHelper = $carrierGroupHelper;
    }
    public function execute(\Magento\Framework\Event\Observer $observer)
    {
        $transport = $observer->getEvent()->getTransport();
        $order = $transport->getOrder();
        $orderDetail = $this->carrierGroupHelper->getOrderCarrierGroupInfo($order->getId());

        if($order != null)
        {
            foreach ($orderDetail as $orderData) {
                $ddate = array_key_exists('delivery_date', $orderData) ? $orderData['delivery_date'] : '';

                $transport['cddeliveryDate'] = date( 'F d, Y', strtotime( $ddate ) );

            }
        }
    }
}```

Answer 1

The described behaviour point to wrong placed the events.xml file in the directory hierarchy. If you want to catch dispatched event globally (in frontend and admin) you need to declare events.xml file under [module_name]/etc directory. In your case it'll be:

app/code/Foobar/ShipperHQDeliveryDate/etc/events.xml