Can you please provide more information? When is the tool run and where from? As the user or admin? What exactly are you trying to accomplish? Are you trying to converted Exchange users mail files to Domino? Just want to confirm.
Other customers have converted their mail files on premises before coming into the cloud, then used the Hybrid data migration feature to move the mail file(s) into LotusLive Notes (so the user was converted before they came into LLN.)
Please provide more detail as to where you get in the process when using nupgrade. Thanks.