Migrator for Notes to Exchange 4.16.1 and 4.16.2.74 (RTM) do not automatically detect Notes 12 Client installed on MNE server.
The following error is logged in EnumNabsWiz when executing Find NABS:
[COMPONENT=ENUMNABSWIZ]
13:49:58 DEBUG: CmdLine: enumnabswiz.exe /NOFINISHED /NOWELCOME
13:49:58 DEBUG: (84) CNotesApi::Init: Enter
13:49:58 DEBUG: FindNNotes()
13:49:58 DEBUG: (593) CNotesApi::FindNNotes: Enter
13:49:58 DEBUG: CNotesApi::FindNNotes: Exit(0.3583 ms.)
13:49:58 ERROR: [8799-111-18-00000000]Notes is not installed