If you've performed the Windows 10 upgrade from unlicensed or pirated version of Windows 7, 8 or 8.1, then you won't be able to activate the new OS. Furthermore, you'll have to deal with the usual restrictions incurred by the use of a non-genuine version of Windows (no security updates, warning messages...)
If you'd like to take advantage of the all features offered by Windows 10, you'll need to activate it with valid product key.
How To Activate Windows 10
Activating Windows 10 on your PC is a breeze. The first step is to purchase a valid product key from the Microsoft Store or any authorized reseller based on the current version of Windows 10 installed on your PC.
Once done, click on Start > Settings > Update & Security > Activation. Next, click Change product key, enter your new product key and follow the onscreen instructions.