I have the same issue, the app remains unaware whether the code is entered and subscription is redeemed from App Store or not. The user has to close the app and restart it and again enter the iCloud password which then detects that a subscription is active, then it lets the user use the app. Is it the same case for you? I am developing in Flutter by the way.

If yes and you've found a solution, please help me also.

Thank you very much