How do you prepay for an item on a Purchase Order?

I have Document IDs 626688.1, 626921.1, & 627107.1 and still do not understand how to help my A/P Department prepay for a product from an invoice and then upon receipt voucher that same invoice against the receipt. I had set up the PrePayment Vouchering in A/P previously as described in Document ID 627107.1 and it worked fine but it did not involve Inventory and a Purchase Order. So they used the PrePayment Voucher to voucher a PrePayment of an Inventory Item and now the system won't accept the Invoice Number in the Voucher Match program (P4314) as it was used in the PrePayment Voucher program (P04105). So I attempted to look in the documentation for what was done wrong and for some reason the Documents don't seem to correspond in my opinion. (JDE World A9.2.1)