Hello Nakul,
Thanks for your reply. Yes, I came across this recommendation before and I will try. However, when solving a problem I want also to educate myself a bit. Now, the question is:
1. Is the problem (i.e. failed invoice duplicity check) really caused just by missing message? Is it proven that adding the message will bring back the required functionality?
2. This is the standard SAP functionality. What is the cause that the message is not in the system? When searching for the solution I found several records of the same case.
Anyway, I will try and report back.
regards,
Jan