this fix is for VLC activation:
Close the activation window and all Office apps.
Open regedit (using run or type it at the start menu)
It is always very important to make backup of registry or the registry key you are changing or deleting first.(use export under file menu)
navigate to:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Office\16.0\Common\OEM
Edit>Delete.
Do the same with this key:
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Office\16.0\Common\OEM
Close the Registry Editor and start Office again.
resources: