The server has reached the maximum number of sessions it supports.
Any action to correct the problem should be performed on that computer. The server is supporting the maximum number of sessions.
Try the command later. You will not be able to start a session with this server until another user's session has ended. Also, see your network administrator. Your administrator may want to purchase an Additional User Pack for the server or increase the value of the MAXUSERS entry of the server's configuration file.