In the world of IT power users and enthusiasts, this key represents a quest for the "cleanest" possible Windows experience.
If the key is rejected as "invalid," ensure you are running a version of Windows that supports an in-place upgrade to IoT LTSC 2021.
Windows 10 IoT Enterprise LTSC 2021 is a "binary equivalent" to Windows 10 Enterprise LTSC but with different licensing and life-cycle support.