Hi, What is understood is you are trying to add a new agent host. And while doing so you are getting connection refused. If you are trying to install the agent manually , then check if the agent RPM version is same as of Ambari server using command : rpm -qa | grep -i ambari.  Check if the connecting port between agent and server is open and is not blocked.  Check the agent.ini file has the correct ambari server hostname.  ... View more