1. Please open PrestaShop root directory on server. Make sure that you have permission to modify PrestaShop source files.
   
2. Go to classes/order directory, and open Order.php.
   

3. Find function setWsShippingNumber($shipping_number) (around line 2215), and insert the following line as marked:
   

   public function setWsShippingNumber($shipping_number)
       {
           $id_order_carrier = Db::getInstance()->getValue('
   			SELECT `id_order_carrier`
   			FROM `'._DB_PREFIX_.'order_carrier`
   			WHERE `id_order` = '.(int)$this->id);
           if ($id_order_carrier) {
               $order_carrier = new OrderCarrier($id_order_carrier);
               $order_carrier->tracking_number = $shipping_number;
   			$this->shipping_number = $shipping_number;    // <----------Insert this line !
               $order_carrier->update();
           } else {
               $this->shipping_number = $shipping_number;
           }
           return true;
       }
   

4. Find function setCurrentState($id_order_state, $id_employee = 0) (around line 1545), and add following lines to that function:
   

   public function setCurrentState($id_order_state, $id_employee = 0)
       {
           if (empty($id_order_state)) {
               return false;
           }
           $history = new OrderHistory();
           $history->id_order = (int)$this->id;
           $history->id_employee = (int)$id_employee;
           $history->changeIdOrderState((int)$id_order_state, $this);
           $res = Db::getInstance()->getRow('
   			SELECT `invoice_number`, `invoice_date`, `delivery_number`, `delivery_date`
   			FROM `'._DB_PREFIX_.'orders`
   			WHERE `id_order` = '.(int)$this->id);
           $this->invoice_date = $res['invoice_date'];
           $this->invoice_number = $res['invoice_number'];
           $this->delivery_date = $res['delivery_date'];
           $this->delivery_number = $res['delivery_number'];
           $this->update();
   
   		$carrier = new Carrier($this->id_carrier, $this->id_lang);      // <----------Insert this line !
   		$template_vars = array(											// <----------Insert this line !
   			'{shipping_number}' => $this->shipping_number,       		// <----------Insert this line !
   			'{followup}' => str_replace('@', $this->shipping_number, $carrier->url),   // <----------Insert this line !
   		);                                                              // <----------Insert this line !
   
           $history->addWithemail(true, $template_vars);
       }
   

   
   

   '{shipping_number}' should match Tracking Number placeholder in your Email Template. 

   '{followup}' should match Tracking URL placeholder in your Email Template. 
   

   
   

5. Make sure to save Order.php file before you close it.
   

Modify classes/webservice/WebserviceRequest.php:

1. Go to classes/webservice directory, and open file WebserviceRequest.php.
   

2. Find function saveEntityFromXml($successReturnCode) (around line 1371), and insert following lines (around line 1425):
   

   ......
   foreach ($xmlEntities as $xmlEntity) {
               /** @var SimpleXMLElement $xmlEntity */
               $attributes = $xmlEntity->children();
   
               /** @var ObjectModel $object */
               $retrieve_data = $this->resourceConfiguration['retrieveData'];
               if ($this->method == 'POST') {
                   $object = new $retrieve_data['className']();
               } elseif ($this->method == 'PUT') {
                   $object = new $retrieve_data['className']((int)$attributes->id);
                   if (!$object->id) {
                       $this->setError(404, 'Invalid ID', 92);
                       return false;
                   }
               }
               $this->objects[] = $object;
               $i18n = false;
   			
   			if(!empty($this->resourceConfiguration['fields']['current_state'])){    // <----------Insert this line! (Around Line 1425)
   				$prop = $this->resourceConfiguration['fields']['current_state'];    // <----------Insert this line!
   				unset($this->resourceConfiguration['fields']['current_state']);     // <----------Insert this line!
   				$this->resourceConfiguration['fields']['current_state'] = $prop;    // <----------Insert this line!
   			}                                                                       // <----------Insert this line!
   			
               // attributes
               foreach ($this->resourceConfiguration['fields'] as $fieldName => $fieldProperties) {
                   $sqlId = $fieldProperties['sqlId'];
   
                   if ($fieldName == 'id') {
                       $sqlId = $fieldName;
                   }
                   if (isset($attributes->$fieldName) && isset($fieldProperties['sqlId']) && (!isset($fieldProperties['i18n']) || !$fieldProperties['i18n'])) {
                       if (isset($fieldProperties['setter'])) {
   ......
   
   
   

3. Make sure to save WebserviceRequest.php before you close it.