Extra thing before you do all of this command.

[smfthe1199]

After you open the Command Prompt as an administrator:

Type the following command: slmgr /upk. and it'll pop up an message, click on OK.
And now this command: slmgr /cpky, it'll pop up another message, click on OK.
And now type this command: slmgr /ckms, you'll get yet another message, just click on OK.

(Source: a Github Gist article at https://gist.github.com/kimgiftww/6d6242e35ef6e3baa3a6e4fb8f386d0b)