lookup of alternativeServiceIdentifier via CPA-cache failed for channel

Hello together,

in our XI-environment we are faced with the following issue:

The connection between the IS-U system and the XI has been realized using the SM59 on the IS-U sender system.

From the XI our sender system is set up using the RFC-adapter (outbound interface) and the answer (inbound interface) is using the SOAP-adapter. The recipient is communicating with a web service on the customer side (non-SAP-system).

The wsdl-file, uploaded to our XI system has been generated at the customer side.

The following problem occured:

if the request is made for the first time, within the transaction sxmb_moni successfull transmitted/

exchanged messages are visible.

But if we do the same request a second time, the error:

"lookup of alternativeServiceIdentifier via CPA-cache failed for channel ''"

is created.

But: the communication channel mentioned is not existing !!!

Using the note:

we tried to solve the problem but it did not work. The error is still occuring.

I really appreciate your help.

Thank you very much in advance.

Best regards,

Hüdayi and Manuel