Cell-e review for Digital Downloads

For some reason, my customers are not receiving the digital file attachment after purchase. Upon checking on their order in Shopify, I see there is note stating, "This order has no digital attachments" despite me confirming that the file is attached to the product in the settings for download. I am having to send URLs manually. However, when I create an order manually, the details do indicate there is a file attached and the file is sent automatically with an email sent.