Licensing system of the product is based on the checking on what machine you currently run the product. We use Hardware Id for this purpose (this is not Ninja's Machine Id, read more). The Hardware Id of your machine is stored on our server at the moment of activation (when you entered the license key and clicked Activate).
To calculate Hardware Id we use motherboard Id, CPU(s) Id, and serial of your 1st physical drive. Changing motherboard, CPU or 1st physical drive will cause a license checking error.
In this case, contact support, please.