Orders with the status of "Pending" in WooCommerce are orders that have not actually been placed with Sezzle. You will not see any corresponding orders within your Sezzle dashboard, and you will not be receiving funds for those orders.
Orders typically appear in this status when a shopper either decides to not continue with the order (abandons the cart) or is declined for a purchase using Sezzle. If they are declined, they are always given the option to return to your checkout page to use another payment method.
We strongly advise against fulfilling these orders, as these are not orders we will be collecting funds for. For most WooCommerce merchants, once the status changes to "Paid," the order should be fulfilled.
If you are ever unsure about whether an order has actually been placed, we strongly recommend referencing your "Orders" tab within your Sezzle account. This will list all orders that were processed by Sezzle.