Looks like you are trying to connect by SSH protocol to the port 4000.
To fix this you can create a new connection in nxplayer and use
default settings or you can change your current connection:
1. Open nxplayer and find icon of your current connection.
2. Click right mouse button on the connection.
3. From a context menu choose ‘Edit connection’.
4. In ‘Protocol’ field choose NX.
5. In ‘Port’ field set 4000.
6. Accept your changes by clicking ‘OK’ button.
After the fix if you still have problem, please try connect again.
Wait until error shows up in nxplayer and then click ‘Save logs’
button. Please save and send the log file to us.