A callback url needs to be configures in the application used for the integration so that AliExpress can return the "sessionKey". Nevertheless, not everyone needs to configure it, only those sellers that match any of the following conditions:
Sellers that chose the server side approach to obtain the session key.
Callback url configuration guide:
Access the following url .
Click the button "Management" of your application. If there is more than on application click the one that will be used for integration purposes.
After expanding "App settings", click the option "Basic Settings" in the menu on left hand side of the screen.