If your Windows 10 keeps asking for Activation again and again, even though it is activated, by asking you for the Product Key, there are things you need to take a look at to fix the issue.
If you open Windows Settings > Update & Security > Activation, you may see a message – Windows is activated. But just below it, you may see an Activate Windows message, with two buttons, one asking you to Activate the OS copy using the existing product key and another button asking you to Change product key. If you are facing such an issue, go through the post and see if something helps you.
Windows 10 is activated but still keeps asking for Activation
Before you begin, you should keep your Windows product key handy. You could retrieve it by running the following command in an elevated CMD:
wmic path SoftwareLicensingService get OA3xOriginalProductKey
Now you may proceed.
1] Change product key
If you are using the correct product key, click on the Activate button once again. If you have another license key that you want to use, click on Change product key, enter the new one, and select Activate. Does this sort out the issue? If you see an error code, then this post will show you how to Troubleshoot Windows 10 Activation Errors. If you see the same message again, read on.
2] Uninstall & enter again the product key
Uninstall the product key. Then enter the product key anew and try again.
3] Rebuild the Tokens.dat file
The Tokens.dat file in the Windows operating system is a digitally signed file, which stores most of the Windows activation files. Sometimes the Tokens.dat file may get corrupted as a result of which Windows Activation may not take place successfully. Rebuild the Tokens.dat file and then try to activate Windows again.
4] Run Activation Troubleshooter
Run the Windows 10 Activation Troubleshooter and see if that fixes your problem. The Windows Activation Troubleshooter will help you address most commonly encountered activation issues on Genuine Windows devices including those caused by hardware changes.
5] Change activation method
Windows 10 can be activated via two methods, Product Key method, ie. the process of validating software with the manufacturer, and the newly introduced Digital Entitlement. Now if you are logged in with a Local Account, and you do not have a Microsoft Account, I suggest you create a new Microsoft Account and use it to log into your Windows 10 computer.
Having done that, try to Activate your copy. The chances are that you will succeed and you will see a Windows is activated with a digital license message. The idea is to link your Windows license to your Microsoft Account. This should make the problem go away. If you do not succeed, you may click on the Troubleshoot button to bring up the Activation Troubleshooter.
6] Activate by Phone
If you still face this activation problem, you may activate Windows 10 by Phone. Else you should contact Microsoft Support and explain your situation. The Windows Support agent will verify your Windows 10 Product Key and then give you an ID for activating Windows 10 on the new computer.
Hope something helps!