Because the original purchase was a Windows 11 Home digital license, that license will not activate a system currently installed as Windows 11 Pro. A Home key or Home digital license is not compatible with the Pro edition.
Use this path:
- Open Start > Settings > System > Activation.
- Select Troubleshoot.
- If Windows detects a valid digital license for a different edition, it can indicate that the installed edition does not match the license.
- If the device was previously activated and no major hardware change was made, sign in with the same Microsoft account associated with the original purchase.
- Check the original purchase record:
- For a digital copy bought from a Microsoft website, the product key is in the confirmation email.
- If the purchase was a Microsoft Store app Pro upgrade, that uses a digital license instead of a product key.
- If the system must return to Windows 11 Home, install the Home edition. The current Pro installation cannot be activated by a Home license.
- Back up personal files first.
- Create Windows installation media.
- During setup, install Windows 11 Home. If setup shows Select Image, choose Windows 11 Home.
- After installation and internet connection, activation should use the matching Home license.
About 0xC004C008: that error means the product key has already been used on another device. The supported guidance for similar activation failures is to use a different valid product key, wait if activation servers were busy after an upgrade, or contact customer support if activation still does not complete.
If the original license was from a free upgrade path, Windows normally uses a digital license rather than requiring a product key, and it should reactivate automatically on the same hardware.