On the Settings > Store Setup window in the Shipstation account there is an option available on the Actions column to Refresh a store, and a status column that shows the status of the store refresh. The site names have been redacted on this screenshot but you can see that two stores show a good status and two stores are showing an error status.
The error statuses happened because the user attempted to refresh a manual order store. The presence of these errors will not prevent the Pressero ShipStation integration from working as expected. It is advised to not attempt to refresh a manual order store on Shipstation.
Pressero uses the Shipsation OpenAPI to send orders to the Shipstation account. The Shipstation OpenAPI is always listening for inbound requests which include the account credentials specified on the configuration window in Pressero. When Shipstation receives a valid createOrder request it will create an order on your account. This is the method that the Pressero integration uses to push orders to your Shipstation account.
There is no way to trigger or otherwise force ShipStation to download, refresh or request orders from a Manual Order store since Shipstation is just listening for any orders that come through the OpenAPI from Pressero. If you attempt to refresh a Manual Order store you will see an error on Shipstation. Although you do have to setup your store on Shipstation, that store does not need to be connected to Pressero on the ShipStation side, as Pressero is connecting to the store based on the settings you are using on the configuration window on Pressero.