Hi, that key is for when a user starts a new virtual desktop. If users are reconnecting to previously started virtual desktops, the message will not show.
# Specify the message to be shown to the user every time the user
# starts a new virtual desktop on this host.
#
NodeLoginGreeting "Welcome to your NoMachine session
If users are reconnecting and you want to show a custom message, you need something similar to this:
https://knowledgebase.nomachine.com/AR02L00787 – example 2.
There is more info about user scripts in the installation and configuration guides, for example: https://knowledgebase.nomachine.com/DT11R00174#11.5)