Hi,
Glad that the problem is fixed now. Here's a short summary of the issue:
[Problem]
After installing Windows OS via MDT, the user is always prompted to enter the product key at first login.
[Solution]
add the below registry value in Unattend.xml.
reg add "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup\OOBE" /v SetupDisplayedProductKey /t REG_DWORD /d 1 /f
Regards,
Alex