Help with xpath assertion please

Hi,

I am not very technically inclined so excuse me for the basic question.

I am trying to get an assertion working with an xpath and getting nowhere. I have the below xml message and want to use the bold text as me assertion:

<soap:Envelope xmlns:soap="http://www.w3.org/2003/05/soap-envelope" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema">
   <soap:Header>
      <SyncovaSoapHeader xmlns="http://syncova.com/optima/webservices">
         <AuthenticationString>?</AuthenticationString>
      </SyncovaSoapHeader>
   </soap:Header>
   <soap:Body>
      <GetTaskStatusResponse xmlns="http://syncova.com/optima/webservices">
         [b]<GetTaskStatusResult>Failed</GetTaskStatusResult>[/b]     
      </GetTaskStatusResponse>
   </soap:Body>
</soap:Envelope>

I have come up with the below:

declare namespace xmlns="http://syncova.com/optima/webservices"
/soap:Envelope/soap:Body/GetTaskStatusResponse/GetTaskStatusResult

But when I click "Select from current" I get an "Invalid XPath expression" error.

Running the text script gives the below error:

XPathContains assertion failed for path [declare namespace xmlns="http://syncova.com/optima/webservices"
/soap:Envelope/soap:Body/GetTaskStatusResponse/GetTaskStatusResult] : RuntimeException:net.sf.saxon.trans.XPathException: XPath syntax error at char 15 on line 2 in {\n/soap:Envelope/soap:Body}:
    Prefix soap has not been declared

Anybody have any ideas?