If you are importing from an inventory management system automatically, then StockTrim only reads the latest sales orders after your previous import. So if you have since saved other sales orders prior to this then these won't be included by default. Select "Refresh Sales Orders" to re-import all your sales history again.
Note also that we only read orders in the past, not future dated orders. Also items in Unleashed that have a future "Required Date" are not imported.
If you imported via CSV, ensure that the dates are correct in the CSV file, and the import date format (on the load data screen) is correct, and matches the dates in your orders csv file.