Office 2016 / 365 
Windows  7 pro 64bits / Windows 10 pro 64bits
With older versions of Office( 2013, 2010, etc.) works great!
thanks in advance!
UPDATE: If i double click the Ocsinventory.exe, it retrives the key ok. 
The automatic inventory is the one who fails to obtain the key., and so if i run the inventory trough the agent.