SteamVR_Controller.GetPress , GetPressDown, GetPressUp always returns false !

using UnityEngine;
using System.Collections;
using Valve.VR;

public class WandController : MonoBehaviour {
    private EVRButtonId triggerButton = EVRButtonId.k_EButton_SteamVR_Trigger;  
    public bool triggerButtonDown = false;
    public bool triggerButtonUp = false;
    public bool triggerButtonPressed = false;

    private EVRButtonId gripButton = EVRButtonId.k_EButton_Grip;               
    public bool gripButtonDown = false;
    public bool gripButtonUp = false;
    public bool gripButtonPressed = false;

    private SteamVR_Controller.Device controller { get { return SteamVR_Controller.Input((int) trackedObj.index); } } 
    private SteamVR_TrackedObject trackedObj;

	void Start () {
        trackedObj = GetComponent<SteamVR_TrackedObject>();
        Debug.Log("trackedObj: "+trackedObj);                   //trackedObj is never null
	}
	
	// Update is called once per frame
	void Update () {
        if (controller == null)
        {
            Debug.Log("Controler Object ist null");             // controller object is never null
            return;
        }


        gripButtonDown = controller.GetPressDown(gripButton);   //is always false, also when pressing gripButton
        gripButtonUp = controller.GetPressUp(gripButton);
        gripButtonPressed = controller.GetPress(gripButton);

        

        triggerButtonDown = controller.GetPressDown(triggerButton);
        triggerButtonUp = controller.GetPressUp(triggerButton);
        triggerButtonPressed = controller.GetPress(triggerButton);
        Debug.Log("triggerButton: "+ controller.GetPress(triggerButton));  //is always false, also when pressing triggerButton
        Debug.Log("triggerButtonDown: " + triggerButtonDown);              //is always false, also when pressing triggerButton


//content of these if-statements never get activated/run -> also when pressing all Buttons permanently ! 
        if (gripButtonDown)
        {
            Debug.Log("Grip Button was just pressed");
        }


        if (gripButtonUp)
        {
            Debug.Log("Grip Button was just unpressed");
        }


        if (triggerButtonDown)
        {
            Debug.Log("Trigger Button was just pressed");
        }


        if (triggerButtonUp)
        {
            Debug.Log("Trigger Button was just unpressed");
        }

    }
}

This script is attached to ‘Controller (left)’.

Why do the methods ‘controller.GetPressUp(gripButton); controller.GetPressDown(gripButton); controller.GetPressDown(triggerButton);’ etc. always return false ; even though I’m pressing all the Buttons(Trigger, Grip, and all other buttons) on the Vive controller (left) ?

Thanks

I now this is a very old Topic. Nevertheless i wanted to add a solution that (at least for me) works and ansers the question:

void Update () {
		if ( Controller.GetPressDown (SteamVR_Controller.ButtonMask.Grip)) {
			do_something();
		}
		if (Controller.GetPressUp (SteamVR_Controller.ButtonMask.Grip)) {
			do_something_else();
		}
	}

For anyone else who crosses this post and has the same problem I did, this solution did not work for me. Instead after poking around what finally worked for me was this:

 public SteamVR_TrackedController controller;

void Start()
{
controller =  GetComponent<SteamVR_TrackedController>();    
}

 void Update () {
       if(  controller.triggerPressed == true)
Debug.Log("A trigger has been pressed");
     }