We have changed our app from being a Purchased (v1.x) to a Free app(Add Version) and included In-App purchase(v2.x) . We installed our app(v1.x) from the App store and then installed (v2.x) from Test filght. In this version, the buy "In-app purchase" and "Restore" options were provided.
When the Restore button was tapped, the app could not restored.The following was also performed in iOS 9.x and 10.1,and it was successfully restored.
In iOS 10.2.1, when I tap the buy "In-app purchase", it promts to Sign in to iTunes store. After succesfully confirming the respective user credentials, it promts me with a "Confirm In-app purchase" alert. On selecting the "Buy" action, it displays "You've already purchased this. Would you like to get it again for free" alert. After tapping on OK, it is then restored successfully.