Only standard or back order sales orders can be selected (not master orders, repeating orders, or quotes).
Sales orders which are on hold cannot be selected.
StarShip allows you to create a shipment against a sales order which already has an open Invoice against it as long as some items are not fully shipped.
If the sales order has an invalid tax schedule, salesperson, or ship via, it cannot be selected.
StarShip does NOT check whether the customer has exceeded their credit limit.
StarShip does NOT check if paid by credit card and credit card has not been pre-authorized or the pre-authorization has expired.