If the Windows 11 Pro upgrade was bought from Microsoft Store, it normally uses a digital license, not a 25-character product key. The Microsoft account used for the purchase is the license.
For the same laptop after reinstalling Windows:
- Check that Windows 11 Home is activated first.
Go to Start > Settings > System > Activation. - On that same page, confirm the device is signed in with the Microsoft account that holds the Pro digital license.
- Run the Activation troubleshooter. If it shows the option, select Upgrade to Windows 11 Pro and then select Start upgrade.
- If Windows was previously activated with a digital license linked to the Microsoft account, Windows can reactivate automatically after reinstalling the same edition. Since Home is installed and the license is for Pro, the device must be upgraded to Pro for that Pro digital license to apply.
If a Windows 11 Pro product key is available instead of a digital license, use: Start > Settings > System > Activation > Change product key and enter the 25-character key.
If the Pro upgrade was purchased in Microsoft Store, no product key may appear because Store purchases of the Pro upgrade use a digital license.