How do you activate Windows if it is not activating?

Select Start > Settings > Update & Security > Activation , and then select Troubleshoot to run the Activation troubleshooter. For more info about the troubleshooter, see Using the Activation troubleshooter.

How do I manually activate a Windows license?

To activate Windows 10, you need a digital license or a product key. If you’re ready to activate, select Open Activation in Settings. Click Change product key to enter a Windows 10 product key. If Windows 10 was previously activated on your device, your copy of Windows 10 should be activated automatically.