MDN is not signed error

Trying to send a functional ack aback to my trading partner and get the following message. Does this mean the TP is not signing the MDN?

[Jan 5, 2017 3:00:05 PM] 0A40170315970378C64000006E1B3490@SPSCommerce: Inbound MDN is not signed.
[Jan 5, 2017 3:00:05 PM] 0A40170315970378C64000006E1B3490@SPSCommerce: Inbound transmission is a MDN [SPSCommerce - Cas].
[Jan 5, 2017 3:00:05 PM] 0A40170315970378C64000006E1B3490@SPSCommerce: Inbound MDN is the answer to AS2 message "mendelson_opensource_AS2-1483646405309-12@CasAS2_SPSCommerce".
[Jan 5, 2017 3:00:05 PM] 0A40170315970378C64000006E1B3490@SPSCommerce: Inbound MDN state is [processed/error: unexpected-processing-error].
[Jan 5, 2017 3:00:05 PM] 0A40170315970378C64000006E1B3490@SPSCommerce: Inbound MDN details received from SPSCommerce: "This MDN response message is for:
Message id:
From: Casd
Date received: Thu, 05 Jan 2017 20:00:05 GMT"

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Hello service,
you are right, it's recommended, not yet a standard. So it must be disabled if it cause problems.
And problems are with Kingfisher in England and Ferrero in Germany. Enough to not have it in production.

I tried to fix and recompile the sources, but unfortunately I encountered some problems setting up the environment with eclipse. I gave up. b47 is stable enough.