I agree with
@winnielinnie that it's not likely the key, but it might be a symptom of some networking anomaly. I have no idea what.
Have you had a windows network (SMB) up and running prior to starting out with this TrueNAS server?
Actually, I'll repeat here a question of WinnieLinnie's that's still open - please tell us about your server and your windows client where you don't have the credentials dicussed above, full hardware and OS descriptions for each, also for your network.