The Accounts Receivable (A/R) Aging report will only show the total amount of your open invoices. Whereas, your Chart of Accounts' total balance will show the running balance. You can run the Transaction Detail by Account to compare the balances. Let me guide you how.
Also, make sure to choose the correct report period for the balances to match. Here's an article for more information: How To Get Your Aging Reports To Match.
I have this link in case you have other questions about QuickBooks Online (QBO): Help Articles.
Please let me know if you have further question. I'll be here to help.