If you bought Litchi in the Amazon app store and your remote controller uses Android 6 or lower (for example Phantom 4 Pro RC, Crystalsky etc), then you can no longer download Litchi from the Amazon app store since Amazon has dropped support for Android 6 or lower. If you need to reinstall Litchi in such situation, please contact us at support@flylitchi.com and we will send you an APK that you can use instead.