Check the aging report parameters. For example, maybe there are debit balances in the AP account and the report is set up to ignore those. Or could be the report parameters are set to only include age payables that are past due by a certain amount of days so the aging report is ignoring the current payables. If those don't work, throw the raw AP data (payee, amount due and due date) into Excel and create your own report to test against the system aging report.