Invoice Shows as Paid, but has not been Paid

Hello - I have an invoice that is showing as paid, but it's not. When I pull it up under Vendor Inquiry it still shows a balance due. However, when I pull it up under Invoice Data Entry - it is stating is has already been paid. It doesn't even give the option where you can make an adjustment, etc. A box pops up and it just says already paid. I can't even reverse a check, etc. becuase as stated above, it's showing a balance due when I pull it up in Vendor Inquiry. Help!