Please follow the below steps to manually update the status of an invoice, from Unpaid status to Paid from the drop down menu.
1) Click "Auctions" on the far left > Click on "Manage Auctions"
2) Click on the "Name" of your auction.
4) Click "Invoices".
5) Click on the Name the invoice you want to edit is listed as.
6) Select the payment method that you received from the winning bidder. You will be prompted to confirm you are sure before the invoice is marked as paid.