QuickBooks® requires that a customer record be defined before a payment can be recorded for that customer. But when you are first starting to use the QuickBooks® export feature, you may export user payments that do not have a corresponding user transaction record.
In this case, QBD will add the username to its Other Names list instead of the Customer list. The Other Names list can be found on the Lists menu. Other Names can be re-categorized as Customers by editing the name and clicking the Change Type… button.