Windows activation key not working

[Juvanjkin2l]

I bought an activation key for Windows 10 Pro, but it doesn't work. The error code is 0x803FA067. I've been searching through previous support questions for a while but haven't found a solution.
Any help would be appreciated.

 

[Bastet]

From where did you purchase the key? Unless from Microsoft or another authorised seller then the key most likely isn’t legit. Possibly a volume license key which MS have blocked.
If it is genuine then try this:

Activate Windows - Microsoft Support

Learn how to activate Windows using a product key or digital license, check your activation status, and link your Microsoft account.

support.microsoft.com