Ensure that the GL Date of the invoice and Payment are both in open periods; both in AP and GL . Also, other than try to create accounting from the invoice actions TAB, try to ran the Payables Accounting Process, with debug mode set to “YES”. That should generate an exeptions report, which should give you a hint of why its not getting accounted. If you go to view log of the PAP output file, and you carefully scroll through the techy stuff, it should give you a reason some where, or an error as to why its not getting accounted(If you had set the DEBUG mode to “YES").Otherwise, ran the APListh.sql diagnostic script for that particular payment and invoice id, and log a Service Request with metalink. Should get a timely resolution.
BR and Good Luck
Timothy