JBoss ON UI is not starting

Issue

• JBoss ON user interface is not visible;
• server.log states that JBoss is started but user interface is not coming up;

• JBoss ON server.log contains the following message:

  ... WARN  [org.jboss.jca.core.connectionmanager.pool.strategy.PoolBySubject] (ServerService Thread Pool -- 66) IJ000604: Throwable while attempting to get a new connection: null: javax.resource.ResourceException: Could not create connection
  ...
  Caused by: org.postgresql.util.PSQLException: Connection refused. Check that the hostname and port are correct and that the postmaster is accepting TCP/IP connections.
  ...
  Caused by: java.net.ConnectException: Connection refused
  ...
  
  ... WARN  [org.hibernate.engine.jdbc.internal.JdbcServicesImpl] (ServerService Thread Pool -- 66) HHH000342: Could not obtain connection to query metadata : javax.resource.ResourceException: IJ000453: Unable to get managed connection for java:jboss/datasources/RHQDS