Hi tehn,
Can you tell us which NoMachine version did you install on the remote computer? Also, which product did you install on the connecting clients? Are you connecting using the browser?
The NoMachine free version does not support multiple connections.
The NoMachine Enterprise Desktop does support the connection of multiple users to the same physical desktop. Those users will all see and collaborate on the same desktop (more information here: Does Enterprise Desktop allow multiple users to connect to their own individual desktop?).
Feature comparison: Remote access for everyone
Thanks!