NoMachine prevents a shutdown/sleep only when the session is active. Can you please try without an active session?
That’s the one thing that I managed to NOT say, I guess. The computer itself was/is running, but nothing was connected to it that I am aware of – there should not have been an active session unless there is something in the computer install that causes NoMachine’s service to constantly watch for a connection?
I can see that being the case, but can’t find a setting related to it.