You can pull up your Accounts Receivable Aging Detail report. I can add more details about this and guide you how.
Your open balance is showing as 0 because you might have unapplied credit memos. Having unapplied credit memos decrease your open balance.
To view your balances correctly, you can pull up your Account Receivable aging Detail report.In this report, it'll show all your transactions and their balances.
You can follow these steps in pulling up the report:
If you have open credit memos, you can apply them to your invoices to mark them as paid.
Always know that you can get back to us if you have any other concerns.