Error when testing a web service created in XI

Hi experts,

I created a web service in XI to execute a RFC and return its result, but when the WSDL file is tested in XMLSpy, the below error is returned:

<SOAP:Envelope xmlns:SOAP="http://schemas.xmlsoap.org/soap/envelope/">     <SOAP:Body>          <SOAP:Fault>               <faultcode>SOAP:Server</faultcode>               <faultstring>System Error</faultstring>               <detail>                    <s:SystemError xmlns:s="http://sap.com/xi/WebService/xi2.0">                         <context></context>                         <code>RCVR_DETERMINATION.MESSAGE_INCOMPLETE</code>                         <text>Message is incomplete. No Sender found</text>                    </s:SystemError>               </detail>          </SOAP:Fault>     </SOAP:Body></SOAP:Envelope>

It's the first time I use XI, so I've no idea of which extra details I should provide to give a better description of my problem.

Thanks in advance,

André Ramos Souza