Unapplied payments that appear in accounts receivable aging report

I am stuck and wondering how to fix a problem. Here is the situation I found in the books.  Accounts receivable aging shows a negative number for a customer who made a purchase back in 2022.  It appears to be an unapplied payment.  When I look at the customer account detail, the invoice was issued in September and still shows past due, but does not appear on the account receivable aging.  The payment was processed in December but shows in the customer account detail as unapplied. The customer account balance is zero.  The payment does appear in the accounts receivable aging.  When I open the payment and try to apply it to the invoice, I cannot seem to get the open invoice to appear so I can check the box and apply it.  For reference, the payment occurred in Deposited Quick Book payments and was correctly transferred as a deposit to the business owners checking account.  I would sure appreciate any guidance.  Thank you.