Here are the most common reasons that it would not show:
Alternative payment methods (see payment methods)
The customer chooses to check out with an installment service or a wallet service (such as Klarna, Sezzle, Affirm, AfterPay, Apple Pay, Amazon Pay, or Google Pay).
Your store has multi-currency enabled and the order was made in a currency other than your "store currency".
If the order was placed with PayPal, your store may not be approved for PayPal Automatic Payments.
See the PayPal Automatic Payments document for information on how to check this.
You don't have AfterSell enabled as your post-purchase page app in your Checkout settings.
The order was paid for using a Gift Card, COD or it was a $0 (free) order.
The original order contains a subscription product, and the upsold product is also a subscription product.
Your product has inventory tracked and the inventory amount is zero or less.
Your product is in an order for local delivery.
The Shopify Platform is under extreme load.
Get even deeper insights by using the AfterSell "Order Browser" feature.
By clicking into each order, you can learn why the offer was not shown.
Please don't hesitate to message us if you have questions or concerns.