Unable to download . User does not have sufficient privileges UCM

Content

I've tried getting a file with the UCM web service:
https://<UCM_host_name>:<UCM_port>/idcws/GenericSoapPort?WSDL

this is my request:

     <soapenv:Body>
      <ucm:GenericRequest webKey="cs">
         <ucm:Service IdcService="GET_FILE">
            <ucm:Document>
               <ucm:Field name="dDocName">UCMFA00755994</ucm:Field>
               <ucm:Field name="RevisionSelectionMethod">Latest</ucm:Field>
               <ucm:Field name="Rendition">Primary</ucm:Field>               
            </ucm:Document>
         </ucm:Service>
      </ucm:GenericRequest>
   </soapenv:Body>

And the response is this:

<env:Body>
      <ns2:GenericResponse xmlns:ns2="http://www.oracle.com/UCM"&gt;
         <ns2:Service IdcService="GET_FILE">
            <ns2:Document>
               <ns2:Field name="StatusCode">-18</ns2:Field>
               <ns2:Field name="IdcService">GET_FILE</ns2:Field>