Good news - They're ABSOLUTELY NOT missing :-) It's just that Amazon works a bit differently than some other marketplaces as to how they handle their settlements.
You see, as an Amazon Seller your sales accrue over time. While Amazon will sometimes display your sales in certain reports, in reality they only truly remit payment to the Seller AFTER the order is fulfilled. Once the order is marked as fulfilled, only then will Greenback display them as settled transactions.
Keep in mind that this means that the date the item was purchased and the date we actually show it as settled are often two different dates. Greenback always references the actual settlement date in our systems, irrespective of the date when the customer purchased the product on their end.
Please be aware that from the time Amazon "settles" your transactions, there can be a delay of a few hours or more before the settlement data is available for Greenback.