AS2 Async mdn issue in seeburger monitor

Hi PI Experts,

My scenario is  B2B Inbound  Interface.

Partner(AS2)------->PI(7.31)--------->SAP.

MDN:Async

While Partner  sending data from Third Party  to PI   getting below error in Seeburger Monitor.

Error : Could not send ansynchrone MDN to partner!

for  Inbound interfaces from Partner side they did the MDN:Aync  settings .But PI not able to receive the data from Partner ,getting the above error in seeburger monitor.

Could you please help me on this issue ,this is very urgent.

Thanks,

Aadi