BPM (IP) Error: "No object type found for this message [...]"

For your info.

I have searched SDN today for a solution to an error message found in XI message monitor (trx SXI_MONITOR) when sending a message to BPM:

<b>No object type found for this message; check the activation of the corresponding process</b>

Well, I found a lot of threads, but with no good answer for me.

So, here's my self-solution: I was just missing the Interface Determination (really don't know why) bringing from Outbound to Abstract message interface. So XI message was definitely correct.