You are experiencing something weird with Windows 10. You have an activated Windows 10 that is asking for activation. You are still getting notifications that you need to activate it. It is an annoying situation especially when you know you purchased a very good copy of Windows 10.
Here are troubleshooting steps for removing the recurring notification on your Windows 10.
Re-register using Original Product key
Before anything else, make sure you can easily retrieve your Windows product key. Save it on your desktop using a sticky note or a notepad. To access the correct product key that your Windows 10 came with, just open an elevated Command Prompt and type the following command: