Hi,
This indicates that the product_id column in the hikashop_order_product table has been emptied in your database. So the link between the products in the orders and the products themselves has been lost and thus HikaShop cannot retrieve the images.
To fix that, you would have to run a MySQL query in your PHPMyAdmin:
UPDATE #__hikashop_product as p, #__hikashop_order_product as op SET op.product_id=p.product_id WHERE p.product_name=op.order_product_name
where #__ needs to be replaced by your joomla table prefix.