If the error code 0x803F7001, 0x8007007B, it means that a valid license couldn’t be found to activate Windows on your PC. This can happen for several reasons:
This is the first time Windows 10 has been installed on this PC. In this case, you’ll need to provide a valid 25-character Windows 10 product key or purchase a Windows 10 digital license to activate. To buy a digital license online, select the Start button > Settings > Update & Security > Activation , and then select Go to Microsoft Store. In Microsoft Store, follow the instructions to buy a license for Windows
You changed the hardware on a previously activated Windows 10 PC. A Windows license is associated with your PC hardware. If you make significant hardware changes, such as replacing your motherboard, Windows won’t be able to find a matching license the next time you start your PC. If Windows was preinstalled on the PC, then a new license is required if you have made a change such as replacing the motherboard. To purchase a new Windows license, select the Start button > Settings > Update & Security > Activation , and then select Go to Microsoft Store.
If you have a Windows product key you used on your PC before the hardware change, enter it by selecting the Start button > Settings > Update & Security > Activation and then selecting Change product key.
In addition, Microsoft provides an exception path for transferring a Windows License after a hardware change. You’ll need to be signed in to the same Microsoft account before making the hardware change and to use the exception path.
To access this exception path, the Start button > Settings > Update & Security > Activation and then select Troubleshoot. If the troubleshooter can’t resolve the issue, you’ll see a link to reactivate after a hardware change. Select it to follow this path.