PlayerPrefs not saving on Android/iOS Phone but saving on Unity Editor

I am using Unity 5 on iMAC. I have faced strange but true unknown issue with player prefs.

Issue :

On Unity Editor - I have stored integer value in player prefs that works fine in UnityEditor, and when i restart my game in unityEditor then It was saved and i can retrieve that older saved player prefs's value.

On Android/iOS Device - I have run that same code with device then behaviour will changed.During running game player prefs works fine and i can set and get that value. But when i restart the game then i lost that value and can't retrieve that saved value another time.

I am tired to solve that issue, but i can't get success.

Anyone know solution about this unknowing behaviour of player prefs ?

Thank you in advance.