AS2 Seeburger Error

Hello,

We are using an integration in which one new partner is sending data to PI via see burger AS2 adapter.  But while sending a test message he is getting below error:

"com.seeburger.ediint.edi.EDIMessageException: cannot decrypt message

(certificate or private key missing)"

1) Coomunication is from ABC-->AS2-->PI-->RCV

2) All certificates has been installed properly in NWA

3) AS2ID has been assigned properly.

4) sender party has turned off encryption and signing at their end but still he is getting same error.

Are there any other AS2 parameter settings in the NW layer??? Or there anything on an additional level that can be defined on party level??

Please help. Prompt and quick response will be highly appreciated.

Cheers!!

Ankit