Hi, accounting549.
Thank you for posting your concern here in the Community. I'm here to share some details about why the AP Aging report does not match to Balance Sheet report.
Disagreement between the two reports it's because of the future payments made to the current bill. The AP Aging report does not include bills that are marked as paid, while the balance Balance Sheet and the Accounts Payable Aging Detail reports are correct because the bill is no longer open.
You can see this article for more information: About Balance Sheet and Accounts Payable Aging report disagreement.
I've also added this article that'll help you customize reports and basic info in QuickBooks Online.
Please do get back on this thread if you need further assistance in running reports. I'm always here to help you.