I’m sorry, the message indicates that the MDN reports back on an error from the partner. This means that the authentication failed on the partner’s side. You can see this by looking at the MDN content. There should be a message in it like “The signature of the message sent from [xxxx] for [yyyy] could not be verified”.
Make sure you use the right private key to sign the message, the partner should use your public key to verify.
Make sure on the service wm.EDIINT:send that the parameter “Type” is set to something you agreed upon with your partner (Signed, SignedAndEncrypted, etc.).
If you use a CA chain in a CA directory, retart the IS after adding the certificates.
Is Gentran Drummond certified?