1. Open Powershell as administrator
2. Enter the following command
slmgr -ipk <Your product key here>
3. Then enter this command
slmgr -ato
example:
slmgr -ipk 82312-ABCDE-AB89X-1234GF-567YA
slmgr -ato
Note the second command can take a minute, just be paitent.
Above method not working
Reinstall windows using this ISO : https://download.livezentech.cc/windows/11/Win11_EnglishInternational_x64.iso
and apply activation key and update