Hm... that's strange, I haven't heard of that problem before. Have you tried searching 'permission manager' on your phone? It should be under the apps section. From there should be a files and media section. There it shows you exactly what apps are and aren't allowed the files and media permission. And have you tried completely removing the game from your phone, cache, apk and all, and reinstalling it? It should have asked for permission upon first launch.