Api bilgilerini kontrol ettim her hangi bir sorun görünmüyor. Tam olarak kullandığım kod aşağıdadır.

abc.php

Class N11 {
    protected static $_appKey, $_appSecret, $_parameters, $_sclient;
    public $_debug = false;
    
    public function __construct(array $attributes = array()) {
        self::$_appKey = $attributes['appKey'];
        self::$_appSecret = $attributes['appSecret'];
        self::$_parameters = ['auth' => ['appKey' => self::$_appKey, 'appSecret' => self::$_appSecret]];
    }
    
    public function setUrl($url) {
        self::$_sclient = new \SoapClient($url);
    }
 

  //Stok Güncelleme

  public function UpdateStockByStockSellerCode($products = array())
  {
    

  
    $this->setUrl('https://api.n11.com/ws/ProductStockService.wsdl');
    
    self::$_parameters['stockItems']['stockItem']['sellerStockCode'] = "Stok Kodu";    
    self::$_parameters['stockItems']['stockItem']['quantity'] = "5";
    self::$_parameters['stockItems']['stockItem']['version'] = "";    
    
    $result[] = self::$_sclient->UpdateStockByStockSellerCode(self::$_parameters);
    
        

        return $result;
  
  }


public function __destruct() {
        if ($this->_debug) {
            print_r(self::$_parameters);
        }
    }
    }

guncelle.php

    require_once ('abc.php');
    $n11Params = [
        'appKey' => 'xxxx',    
        'appSecret' => 'xxx',        
    ];
    
    $n11 = new N11($n11Params);
    
    


    
$productList = $n11->UpdateStockByStockSellerCode();
print_r($productList);