Hi,
Please ensure that the consumed WSDL has a target namespace set (edit the WSDL).
You will probably need to download the WSDL and not consume the WSDL directly from the SAP Service.
See e.g.: biztalk-2010-error-consuming-wcf-service-metadata-object-reference-not-set-to-an-instance-of-an
Br,
Leo