Verify signed xml

I try to veriyf a signed xml using the built-in service

I pass the following inputs to the service
xmldata, signatureSelectors (the xpath of element “Signature” in xmldata) and nsDecls.

I get the following exception
Could not run ‘verifyXML’ [ISS.0086.9248] The signature could not be found.

Anyone has got any explanation for the exception? And how to fix this?

Did you configure the trust and key stores on IS? Can I have a look at your flow service. Before verifying the xml did you sign it successfully using specific algo?