JBoss ON Agent cannot register or connect to the server due to a missing security token

Issue

• After migrating from a virtual machine to another server, agent registration fails with error:

  ERROR [RHQ Agent Registration Thread] (org.rhq.enterprise.agent.AgentMain)- {AgentMain.agent-registration-rejected}The server has rejected the agent registration request. Cause: [org.rhq.core.clientapi.server.core.AgentRegistrationException:The agent [jon-agent.example.com] is attempting to re-register without a security token. Please consult an administrator to obtain the agent's proper security token and restart the agent with the option "-Drhq.agent.security-token=<the valid security token>". An administrator can find the agent's security token by navigating to the GUI page "Administration (Topology) > Agents" and drilling down to this specific agent. You will see the long security token string there. For more information, read: https://docs.jboss.org/author/display/RHQ/Agent+Registration]
  ERROR [RHQ Agent Registration Thread] (org.rhq.enterprise.agent.AgentMain)- {AgentMain.agent-registration-retry}Will retry the agent registration request soon...
  

• How to obtain the agent's security token.

• Unable to re-register the agent.
• Agent failed to start and reports Admin intervention needed due to missing security token