Metric error for the Infrastructure stack plugin

Hi all,
I have installed the host target plugin on our Ops Cebter Enterprise Manager and now I am trying to install the Infrastructure stack plugin. However: I get a metric error:

Metric evaluation error start - oracle.sysman.emSDK.agent.fetchlet.exception.FetchletException: em_error=Failed to perform /opt/EMCC/core/12.1.0.3.0/jdk/bin/java: java.lang.Exception: Ops Center client failed to establish connection with Enterprise Controller: com.sun.xml.ws.api.message.Messages.create(Lcom/sun/xml/bind/api/JAXBRIContext;Ljava/lang/Object;Lcom/sun/xml/ws/api/SOAPVersion;)Lcom/sun/xml/ws/api/message/Message; at oemmp.client.OCClient.main(OCClient.java:63) Exception in thread "main" java.lang.Exception: Failed to perform mapTarget command. Reason: Ops Center client failed to establish connection with Enterprise Controller: com.sun.xml.ws.api.message.Messages.create(Lcom/sun/xml/bind/api/JAXBRIContext;Ljava/lang/Object;Lcom/sun/xml/ws/api/SOAPVersion;)Lcom/sun/xml/ws/api/message/Message; at oemmp.client.OCClient.main(OCClient.java:101)