Dear Prasanna,
It may be silly but, Please check whether the Settlement profile given in the project and settlement profile changed by yourself is same or not.
System will pick the document type assigned in the settlement profile. or kindly share the OKO7 and CJ20N screen shots.
You can do another thing, while executing CJ88 go to Environment->Cust.Setel->there you can select your setllment profile.
Regards,
Praveen