How to trigger a BoxCollider with a RigidBody?

Firstly, let me mention that this is my first project in Unity and that I have no experience before yesterday.

I am trying to create something relatively simple, where there is a button that plays a sound when the mouse hovers over it. I have an object named input_mouse (it contains its own Collider and RigidBody) with the follwing script included:

  #pragma strict
     
     static var mousePos: Vector3;
     var cam: GameObject;
     cam = GameObject.Find("mainCamera");
     
     var trigger: GameObject;
     trigger = GameObject.Find("trigger_pranked");
     function Update(){
          mousePos = cam.GetComponent.<Camera>().ScreenToWorldPoint(Vector3(Input.mousePosition.x, Input.mousePosition.y,1));
          transform.position = mousePos;
     }

This part is working just fine, except that the Z coordinate is interpreted by the program as Z-1. For whatever reason, Unity takes the number "1" from the code above and puts the coordinates of input_mouse as( X-coord,Y-coord, 0). That's off-putting, but tolerable.

Anyway, the real issue for me is getting the button to get triggered. On the button, I have the a script with following code:

 #pragma strict
 
 function OnTriggerEnter(other: Collider){
     Debug.Log("Hello");
     GetComponent.<AudioSource>().Play();
 }

The debug "hello" is just a way for me to be sure that the button is being triggered, and as far as I'm aware it isn't, even though input_mouse enters into its collider zone. As far as I'm aware, this should work, but for whatever reason it isn't. Can anyone explain if I made any errors, or how to fix this?