The plesk license for 10 domains is included with all VPS cloud models. The license is automatically included when you place an order with plesk installed in the beginning as an OS. If you choose another OS initially, the plesk license wouldn’t of been included. It is still available for you to obtain your license, however this would have to be done via the API.
You would use the following syntax:
An order would of been generated automatically, you will need to complete the order, the order it self will be free.