reinstalled W11 as new build, but cant activate

If Windows 11 was previously activated on that device and only the system drive was changed, it should usually reactivate after reinstalling the same edition of Windows 11.

Try this:

1. Check the edition installed:
   • Go to Start > Settings > System > Activation.
   • Confirm whether it is Windows 11 Home or Windows 11 Pro.
   • The installed edition must match the license.
2. If Windows is not activated, run the Activation troubleshooter:
   • Go to Start > Settings > System > Activation > Troubleshoot.
   • If prompted, select I changed hardware on this device recently.
   • Sign in with the Microsoft account linked to the digital license.
   • Select the device from the list, check This is the device I’m using right now, then select Activate.
3. If there is a product key, enter it manually:
   • Go to Start > Settings > System > Activation > Change product key.
   • Enter the 25-character product key and complete activation.
4. If Windows was already activated before reinstalling and the same edition was reinstalled, digital license activation should occur automatically.
5. If activation still fails, check whether the reinstall used the wrong edition. A Home license will not activate Pro.

If the device had a digital license linked to a Microsoft account before the reinstall, the troubleshooter is the main recovery path. If a product key was used originally, entering that key again is the supported method.

References:

• Activate Windows
• Reactivating Windows after a hardware change