If your order hasn’t been imported, please check if the option This product requires shipping is selected before saving your item when adding products in Shopify.
If the issue persists, check if you’ve selected Do not automatically fulfill any of the order's line item in Shopify admin > Settings > Checkout > Order. If so, your order won’t appear in your Printful Dashboard until you manually request fulfillment and Printful accepts it.
If an order fails to get through to Printful, a manual order will need to be placed on your end via your Printful Dashboard.