Your barcode needs to reflect the product ID or alphanumeric value that is saved in the product SKU field in your WooCommerce store’s database. FooSales doesn’t generate barcodes but you can use any online barcode generator to create and print your own barcodes from the product/variation ID or the product/variation SKU as it appears in WooCommerce.
Visit the Barcodes page to learn more about how barcodes work in FooSales