Web service scenario - Missing or Invalid Receiver Agreement

Dear,

We are on SAP PI 7.11 SP11 and facing a problem with a synchronous scenario SOAP <-> SAP PI <-> ABAP proxy.

The Service Interfaces contain multiple operations and operation/message mappings are in place.

Also, configuration on the ID side is done.

The WSDL is retrieved from the sender agreement and imported into soapUI.

All seems there and the cache is ok, but still we face the error Missing or Invalid Receiver Agreement in the message monitor.

I already found OSS note 1739173, describing the problem, but that seems to be for asynchronous messages only with QoS EO and EOIO.

Or do we need that anyway?

Any leads what could solve this strange problem?

thanks a lot.

Dimitri