Karlie here from the Shopify Guru Team! Can you tell me some more details about your customer's order? Did they put the order through online? What payment gateway did the customer use to put their order through with? Can you tell me what your .myshopify.com URL is so that I can take a look at your orders for you? You should see any orders put through customers come into your Shopify Admin> Orders section.
If you're not seeing the order show up in your Shopify Admin> Orders section then the order has not been placed. If the customer is saying that they had put through the order, then you can ask to see the statement on their credit card (while having them hide any sensitive information) to see if the transaction has gone through. You can also check your Shopify Admin> Orders> Abandoned Checkout section to see if the customer may have not completed the checkout process all the way through to the end.
I would recommend making sure that your payment gateways are set up correctly so that customers can process their credit card payments. You can use our guide to make sure that your payment gateway is set up accordingly. You can see your payment gateway settings by going into your Shopify Admin> Settings> Payment Providers section.
I’m having this same problem. The order did not show up in my store but a customer told me she ordered. So I had my notifications sent to me email and her order was there! But when I clicked on view order it says it can’t be retrieved. Why can’t I retrieve orders sent to my email? Why wasn’t the sale on my dashboard?