As long as Pio receives the shipment information from ShipStation before picking the order in Pio, the shipping label will be available when the order is fulfilled.
If you experience that the shipping label is not available when the order is picked and fulfilled in Pio, please try the following.
Manually refresh ShipStation orders
Before picking starts in Pio for the day, log in to your ShipStation account and manually refresh and fetch orders in ShipStation.
This process is also be triggered automatically from Pio, however, Shopify orders may still be received by Pio before they are processed by ShipStation.