GeekSeller will not send orders to a fulfillment service if they come to our system as fulfilled. If you want to have GeekSeller handle order fulfillment for your Shopify orders (sending orders to a 3PL), you need to disable automatic fulfillment of paid orders.
From your Shopify account, Make sure that under Settings > Checkout > After an order has been paid, you have this option selected: “Do not automatically fulfill any of the order’s line items.”