Looks like you don’t have enough disk space. What you need to do is have a clean of your server and make some space on your server host.
System requirements necessary for NoMachine software products are provided on the download pages of each product, so for example, Terminal Server, https://www.nomachine.com/download/download&id=55, and also in the relative Installation Guide, “Prequisites” section. For TS we indicate general guidelines of 1 GB RAM and 195 MB free disk space.
NoMachine software is installed by default in /usr/NX so you must guarantee that the partition where you have installed it has the amount of space that we indicate. If you can’t clear up space on that partition for whatever reason, you can install it in a different location (/opt/NX) on a different partition, see the Installation and Configuration Guide paragraph 3 for further details about that https://www.nomachine.com/DT04O00139#2.3. Simply make sure that the new location on the alternative partition has enough space.