I am getting this error message when I try to authenticate new user. Please see the below request and response xmls
 
<?xml version="1.0" encoding="UTF-8" standalone="yes"?><ns2:messageType xmlns:ns4="http://www.webex.com/schemas/2002/06/service/trainingsession" xmlns:ns3="http://www.webex.com/schemas/2002/06/service/trainingsessionqtiasi" xmlns:ns2="http://www.webex.com/schemas/2002/06/service" xmlns:ns10="http://www.webex.com/schemas/2002/06/service/supportsession" xmlns:ns9="http://www.webex.com/schemas/2002/06/service/user" xmlns:ns8="http://www.webex.com/schemas/2002/06/service/meeting" xmlns:ns7="http://www.webex.com/schemas/2002/06/service/attendee" xmlns:ns6="http://www.webex.com/schemas/2002/06/service/trainingsessionqti" xmlns:ns5="http://www.webex.com/schemas/2002/06/service/session" xmlns="http://www.webex.com/schemas/2002/06/common"><ns2:header><ns2:securityContext><webExID>xxxx</webExID><password>xxxx</password><siteID>xxxx</siteID><siteName>xxxx</siteName><partnerID>g0webx!</partnerID></ns2:securityContext></ns2:header><ns2:body><ns2:bodyContent xsi:type="ns9:authenticateUser" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"/></ns2:body></ns2:messageType>


XML Response

<?xml version="1.0" encoding="UTF-8"?><serv:message xmlns:serv="http://www.webex.com/schemas/2002/06/service" xmlns:com="http://www.webex.com/schemas/2002/06/common"><serv:header><serv:response><serv:result>FAILURE</serv:result><serv:reason>validation: unable to instantiate com.webex.xmlapi.service.binding.AuthenticateUser; java.lang.ClassNotFoundException: com.webex.xmlapi.service.binding.AuthenticateUser</serv:reason><serv:gsbStatus>PRIMARY</serv:gsbStatus><serv:exceptionID>999999</serv:exceptionID></serv:response></serv:header><serv:body><serv:bodyContent/></serv:body></serv:message>