3147653 - Cannot decrypt message: java.lang.IllegalArgumentException: the message is not encrypted for Version: 3

While triggering iflows from 3rd party system using the AS2 Adapter in CPI, you are getting errors below.

MPL:
StartTime           = Sat Nov 06 22:02:04.073 UTC 2021
  StopTime            = Sat Nov 06 22:02:04.409 UTC 2021
  OverallStatus       = FAILED
  IntermediateError   = true
  LastError           = Validation failed in AS2
  LastErrorModelStepId= MessageFlow_75
  Node                = 0

Segment:
   AS2 Incoming Message Log:
     StartTime           = Sat Nov 06 22:02:04.073 UTC 2021
     Status              = PROCESSING
     AS2  Exception      = Cannot decrypt message: java.lang.IllegalArgumentException: the message is not encrypted for Version: 3
Serial number:       XXX
Serial number (hex): XXX
Signature algorithm: sha256WithRSAEncryption (XXX) 
Issuer: CN=DigiCert SHA2 Secure Server CA,O=DigiCert Inc,C=US
Valid not before: Wed Sep 29 00:00:00 UTC 2021
      not after: Thu Sep 29 23:59:59 UTC 2022
Subject: CN=XXX.cpi.hana.ondemand.com,O=SAP SE,L=Walldorf,ST=Baden-Wuerttemberg,C=DE
RSA public key (2048 bits):
public exponent: 10001
modulus: 877495647bc2e01a9fabbe7a7...

   Segment:
      Status event fired by adapter AS2 Sender:
        StartTime           = Sat Nov 06 22:02:04.395 UTC 2021
        Status              = FAILED
        ChildCount          = 3
        Error               = Validation failed in AS2
        ModelStepId         = MessageFlow_75

   AS2 Sender MDN Outgoing:
     StartTime           = Sat Nov 06 22:02:04.295 UTC 2021
     ChildCount          = 2
     ModelStepId         = MessageFlow_75
     StepId              = MessageFlow_75#1636236124295
     Activities [
      {Activity=logAdapterProcessing, StartTime=Sat Nov 06 22:02:04.295 UTC 2021}
     ]

• SAP Integration Suite
• Cloud Integration

Cannot decrypt message, java.lang.IllegalArgumentException, IllegalArgumentException, the message is not encrypted for Version, Validation failed in AS2, SAP Cloud Integration, SAP Integration Suite, SAP Cloud Platform Integration, Cloud Platform Integration, SAP CPI, CPI, SCPI, HANA Cloud Integration, HCI, SAP HCI, tenant, iFlow, Integration Flow , KBA , LOD-HCI-PI-RT-B2B , B2B Adapter , LOD-HCI-PI-RT , Integration Runtime , Problem