We have an IAP setup with a free trial. In sandbox, we see the expected trial period for this product ID. In production (and when I build locally using Release config), .introductoryPrice for the same identifier is nil. I have verified that the IAP is setup in AppStore. This is a product ID that's been around for quite some time, I believe the only recent change was editing the Subscription Group it belongs to but no edits to the IAP itself.
Where could the problem be?
In-App product should be processed separately with application in production after AppStore review.
If you change or edit IAP product settings, it may take up to 24 hours of processing time.
So I believe your IAP product have a introductory price Now because 3 days passed.