Some permission gets reset on iOS app update from Appstore.

I have iOS app created using react-native and deployed it on Appstore few days back. After that i uploaded new version of same app on Appstore and updated my app in iPhone.Before update of app, i had granted required permission but after update of app in iPhone some of the already granted permission are reseted. It's worked when app reinstalled. My question is that why did it removed granted permission on update ?