We show all of your promos in AMZPing.
You probably don't see the discount applied yet, because the order is still Pending on Amazon Seller Central.
If it’s still pending, we have no data yet from Amazon. Seller Central does not show the real price the customer paid, until the item ships. We don’t know which promos were applied either, at that point.
So until it’s pending, we use the regular price from your Product settings. We want to show some data instead of showing zeros, so we choose to display the price we see on the listing.
As soon as it’s shipped, we will get the correct price from Amazon with discount, and update the app to show the new one right away.