The server is setup to limit to four (4) connection attempt per minute, this is to discourage SSH brute force attempt for security purpose. If if it seems to take a long time to connect after you made multiple connection attempts quickly, you can just cancel out and try to log back into psnxserv in 1 to 2 minutes.
If you have disconnected your session without logging out and try to reconnectto nomachine, after once you hit the connect button, you will see the following dialog box. You can create a new session by selecting 'Create a new desktop or custom session' or you can reconnect to your existing session. If the existing session failed to reconnect, you can right-lick on the icon representing your previous session and select Terminate session. And then click on 'Create a new desktop or custom session' and select 'Create a new virtual desktop' to click on continue.