Magento – Notify for Quantity Below in Magento 2

You can try below code for cancelling an order.

$orderModel = Mage::getModel('sales/order');
$orderModel->load($orderId);
if(!$orderModel->canCancel()) {
$orderModel->cancel();
$orderModel->setState(Mage_Sales_Model_Order::STATE_CANCELED, true)->save();
$orderModel->save();
}

In your code, actual code is missing for cancel the order, you had never called cancel() function of class Mage_Sales_Model_Order

In magento direct email not sending to the admin. Magento show low stock report at Reports > Product > Low stock

For Magento 2.2.x Admin Low Stock Notification email Free extension available in github https://github.com/bharat2762/magento2-admin-low-stock-notification

For Magento 2.3.x Admin Low Stock Notification email Free extension available in github https://github.com/bharat2762/magento2.3.x-admin-low-stock-notification

heck this one. It will help.