Problem between BC-SAP and ES

I’m running Business Connector 4.6 and Broker v5.

When invoking my BC (business connector) service to SAP from the BC-IDE or via a URL it works fine.

But when I invoke the service from ES (Enterprise Server) to BC and then to SAP, the SAP does not return any data to BC. Looks like nothing gets written to the pipeline.

Any idea ?