Hi,
Is it possible to update NoMachine without terminating sessions?
No. You will be disconnected because updating requires the stop of all NoMachine services which will be restarted once the update has been completed. You will then be able to reconnect.
Please refer to this article for more details:
How to remotely update NoMachine
https://knowledgebase.nomachine.com/AR05S01123
If I don’t update the NoMachine is there any issue with the existing sessions?
Whereas we always recommend users keep the NoMachine software updated to the latest version which means the latest bug fixes have been installed, including important security updates, if the software is working well for you, you aren’t forced to install the latest version.