Fragment no longer exists for key FragmentStateAdapter with Viewpager2
Using viewpager2 with FragmentStateAdapter has a similar behaviour than FragmentStatePagerAdapter
Actually there are two ways of solving this problem
First one is seting setSaveEnabled() to false into our viewpager2
viewpager2.setSaveEnabled(false)The other one is overriding restoreState at our adapter and return null
Check : https://developer.android.com/reference/androidx/viewpager2/adapter/FragmentStateAdapter
My problem solved with implementing new Navigation Component. It itself handles fragment transition. Anyone who across with this problem can change their navigation method.
All you have to do is to set your viewpager2 in the layout file with the following property
android:saveEnabled="true"