PlayerPrefs works fine in Unity Editor but not on Android

Hey there! I'm using PlayerPrefs to store my data in my game. (it is a simple level unlock system) So my Problem is it works fine in unity Editor but on Android it doesn't work! :( I dont know why and i've already tried what was written here in the forum but nothing works ! Please can anyone help me!? I want to publish the game but without the level unlock system it makes no sense because it is a Jump and Run game. Sry for my english and thanks in advance! :)