Message not found for ERS

Hi gurus,

I am trying to create credit memos for our vendors using MRIS, but I always get an error saying "Invoicing plan: No message was found for partner 9990004/company code 1000".

I created the following message condition record for message type INS:

1000 rs 1 3

The vendor has the roles LF and RS.

It works in IDES with exactly the same settings. What am I missing here?

Thanks in advance

Alicia