Do a credit memo.

You need to look at the raw data in the AP_OpenInvoice file and see what the balance is. Based on what you have said I suspect that when you voided the check you did not recall the invoice but rather just posted to the GL account used on the invoice. You would need to adjust the invoice and use the same GL code to bring a balance to the invoice so you can pay again.

My guess: the payment was reversed without recalling invoices, leaving them as "paid".

Thanks, that solved the problem!!