XPATH search in SOAP request

I'm trying to change a request under a testCase in SoapUI using a groovy script, which goes like this:

def groovyUtils = new com.eviware.soapui.support.GroovyUtils( context )  

// get XmlHolder for request message def 
holderRequest = groovyUtils.getXmlHolder( "createUser#Request" )

holderRequest["//IName"] = "TEST"

holderRequest.updateProperty()
context.requestContent = holderRequest.xml

Normally it would work but not with a particular SOAP request, as the XPATH is never found, I tried searching for it in with this tool http://ift.tt/1fZPmxG and confirmed that the node can't be found, what could be the cause of this behavior with this particular request?

<soapenv:Envelope xmlns:soapenv="http://ift.tt/sVJIaE" xmlns:tws="http://ift.tt/1sRvkPf">
   <soapenv:Header>
      <wsse:Security soapenv:actor="http://ift.tt/1sBaVwY" soapenv:mustUnderstand="1" xmlns:wsse="http://ift.tt/LRW8Ij">
         <wsse:UsernameToken>
            <wsse:Username>RegOff</wsse:Username>
            <wsse:Password Type="http://ift.tt/1aTA7XU">RegOff</wsse:Password>
         </wsse:UsernameToken>
      </wsse:Security>
   </soapenv:Header>
   <soapenv:Body>
      <tws:InsertRequest xpath="/TWS/EP/PU" xmlns="http://ift.tt/1sRvkPf">
           <tws:data>
            <User dname="CN=Prueba de firma 25, OU=Tecnologia, O=Certicamara S.A">
            <Description>TX_ARCH_TEST_1</Description>
            <IName>0</IName>
            <Language>0</Language>
            <CName>
                    <Title>Sr.</Title>
                    <FName>Ususario</FName>
                    <Surname>de Firma</Surname>
            </CName>
            <OName>
                    <Title>Administrador de Infraestructura</Title>
                    <OU>Tecnologia</OU>
                    <O>Certicamara S.A</O>
            </OName>
            <SName>
                    <UID>TX_ARCH_TEST_1</UID>
                    <Passwd>{x-sha256}bkS45P9iX2mASGwFZWN7GtJ6NzDae3wYdRScSUu9epo=</Passwd>
            </SName>
            <Contacts>
                    <Work>
                    <Mail>trustedx@certicamara.com</Mail>
                    <Phone>+34 93 508 80 90</Phone>
                    </Work>
                    <Home/>
            </Contacts>
            <Certificates/>
        </User>
         </tws:data>
      </tws:InsertRequest>
   </soapenv:Body>
</soapenv:Envelope>