OnMouseDown don't work

I use this script:

using UnityEngine;
using System.Collections;

public class mouse : MonoBehaviour 
{
	
	 void OnMouseDown()
	{
	
	Debug.Log("ok");
	
	}
	
	
}

It’s work only on computer (PC) but does not work on the tablet, what is wrong?

I found this existing question that should help explain your troubles and the solution to using OnMouseDown on a tablet.

Are you looking at the logcat while you’re running your game? Because Debug.Log is not going to give you a popup message or anything like that. Just issue the following from your terminal while the device is connected and the game is playing:

adb logcat -s Unity

Then you will be able to see log messages when you use OnMouseDown(). Unity gives warnings about this method, but I’ve never had any problems in the game so it might just be a legacy warning…