<observer name="sales_order_save_after" instance="HawkOrderFlowObserverSalesOrderSalesOrderAfterSave"/>

namespace HawkOrderFlowObserverSalesOrder;

use MagentoFrameworkEventObserver as EventObserver;
use MagentoFrameworkEventObserverInterface;

class SalesOrderAfterSave implements ObserverInterface {

/**
 * @var MagentoFrameworkMailTemplateTransportBuilder
 */
protected $_transportBuilder;

/**
 * @var MagentoStoreModelStoreManagerInterface
 */
protected $_storeManager;



public function __construct(
    MagentoFrameworkMailTemplateTransportBuilder $transportBuilder,
    MagentoStoreModelStoreManagerInterface $storeManager,
) {
        $this->_transportBuilder = $transportBuilder;
        $this->_storeManager = $storeManager;
    }

public function execute(MagentoFrameworkEventObserver $observer)

    {

        $order = $observer->getEvent()->getOrder();
        $last_orderid = $order->getId();
        $order_status = $order->getStatus();

        if($order_status == 'viewed_by_admin') {
                $store = $this->_storeManager->getStore()->getId();
                $transport = $this->_transportBuilder->setTemplateIdentifier('3')
                    ->setTemplateOptions(['area' => 'frontend', 'store' => $store]);
                return  $transport;;
    }

}