We have an SUPIA balance for a supplier in which half was matched on a supplier invoice.  The remaining credit is reflected on the Suppliers account.  When we go to apply the remaining amount, we receive a message saying the invoice is fully matched.  Steps taken:

Created an advanced invoice connected to a payment schedule.

Advanced invoice was paid.

Applied 50% of the advanced invoice to the first payment.

tried to apply the remaining 50% to the second invoice and receive the message.

We have checked the Supplier analysis and it shows an available credit for the supplier. This is tied to a payment schedule and the payment schedule shows a fully matched. 

Not sure where else to look.  we are on apps 9

Any assistance would be appreciated.