ReactNative Flatlist onEndReached not working

In my case the problem was with nativebase <Content>. It was creating problems when <FlatList> was used inside it. Solution :

<Content
  style={{flex: 1}}
  contentContainerStyle={{flex: 1}} // important!
>

Source : https://github.com/GeekyAnts/NativeBase/issues/1736

There is an issue for that here: https://github.com/facebook/react-native/issues/14312. Looks like a lot of people are experiencing the same. There is a suggestion to change the onEndReachedThreshold to value bigger that 0, for example: 0.3.