unity why playerprefs do not werk on mobile code example

Example: playerprefs not working on android

// Make sure that it has a default value, like 0 for example

public float Highscore;

public void Start()
 {
     Highscore = PlayerPrefs.GetFloat("HighScore", 0); // like this
 }


public void Start()
 {
     Highscore = PlayerPrefs.GetFloat("HighScore"); // not like this
 }