Implementing IPointerClickHandler interface does not seem to work

I have just run into this. By implementing IPointerUpHandler and IPointerDownHandler with empty methods, the OnPointerDown method was invoked as expected.

 using UnityEngine;
 using UnityEngine.EventSystems;
 
 public class MyClickableBehaviour : MonoBehaviour, IPointerClickHandler, IPointerDownHandler, IPointerUpHandler
 {
     public void OnPointerDown( PointerEventData eventData )
     {
     }
 
     public void OnPointerUp( PointerEventData eventData )
     {
     }
 
     public void OnPointerClick( PointerEventData eventData )
     {
         Debug.Log( "Clicked!" );
     }
 }

IPointerClickHandler Not Working Checklist

1. Added EventSystem game object to scene (Create -> UI -> Event System)

2. Camera has a Physics Raycaster (Select Main Camera, Add Component -> Event -> Physics Raycaster)

3. Selectable object is a MonoBehavior-derived class that implements IPointerClickHandler, IPointerDownHandler, and IPointerUpHandler (see accepted answer).

4. Selectable game object includes selectable object MonoBehavior script.

5. Selectable game object includes a collider (box, mesh, or any other collider type).

6. Check Raycaster Event Mask vs. game object's Layer mask

7. Verify no collider (possibly without a mesh) is obscuring the selectable game object.

8. If collider is a trigger, verify that Queries Hit Triggers is enabled in Physics settings.

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This list covers all the most common issues (Adding this list for posterity as this problem continues to trip me up every time I start a new project).

I had this issue as well what I had to do was add a Physics Raycaster script to my camera via the add component and searching "Physics Raycaster " every thing worked after that.

If your component is inside a canvas, another solution is to add a Graphic Raycaster component on the component to be clicked.

Add a collider to your game object.

I was stuck on this as well. I had a Physics 2D Raycaster component attached to my main camera, and an EventSystem added to my scene.

My game object implemented the pointer handler interfaces, but what was missing for me was the (Box) Collider. Once I added that to my game object then pointer event handlers were working.