There is this documentation page that describes standard API for FHIR to SDA transformation.

Given the error message, I'd guess that Penn.EDT.Messages.ODSGPStatus class is not XML enabled, i.e. it does not inherit from %XML.Adaptor.

And you'd get an empty response anyway as you never assign anything to pResponse's properties.

One more issue is that argumentless reader.Next() call doesn't seem to make any sense. Maybe you meant reader.Next(.obj).

Also your code does not assign anything to ..Status variable, so why logging it?

Regards,
Dmitry