rigidbody not moving

Hey guys, i'm new to unity but I have android studio experience looking to see how the game industry is !

So i have a ball which is a rigidbody with a circular collider which is located between two walls. The ball is moved to the right when right arrow is pressed and left when left arrow is pressed with transform.position . The initial problem was that the ball was going through the walls even though it shouldn't, because I was using transform.position instead of rigidbody.moveposition which was messing with the physics engine (from what I read here). Now I am trying to use rigidbody.moveposition but the object is not moving anymore :

Here's a video to help you guys get my situation, everytime you hear a fairly loud bang it means i'm hitting either left or right mouse on keyboard :

http://screencast.com/t/7SYxQXfCwMeZ

(Script attached to the ball)

 using UnityEngine;
 using System.Collections;
 
 public class ballscript : MonoBehaviour {
     
     public Vector3 target = Vector3.zero;
     public Vector3 velocity = Vector3.zero;
     public float smoothTime = 0.3F;
     public bool right = false;
     public bool left = false;
     public Rigidbody rb;
     
     public float health = 100;
 
 
     // Use this for initialization
     void Start () 
     {
         rb = GetComponent<Rigidbody> ();
     }
 
     IEnumerator Example() {
         yield return new WaitForSeconds(0.0525f);
         left = false;
         right = false;
     }
 
     // Update is called once per frame
     void FixedUpdate () 
     {
 
 
 
         if (right == true) // OBJECT DOESN'T MOVE.
         {
 
             target.x = rb.position.x + 18;
             target.y = rb.position.y;
             target.z = -1;
             rb.MovePosition(Vector3.SmoothDamp (transform.position, target, ref velocity, smoothTime)); 
 
             StartCoroutine(Example()); // NEVER CALLED.
 
         }
 
         if (left == true) // OBJECT DOES MOVE.
         {
 
             target.x = transform.position.x - 18;
             target.y = transform.position.y;
             target.z = -1;
             transform.position = Vector3.SmoothDamp (transform.position, target, ref velocity, smoothTime); 
             StartCoroutine (Example ()); //CALLED.
 
         }
 
 
     }
 
 
     void OnBecameInvisible()
     { 
         Time.timeScale = 0;
         Destroy (gameObject);
         Debug.Log ("BALL HAS BEEN DESTROYED");
     }
 
 
     void Update()
     {
 
         if (Input.GetKeyDown (KeyCode.RightArrow)) 
         {
 
             right = true;
         }
 
         if (Input.GetKeyDown (KeyCode.LeftArrow)) 
         {
             left = true;
         }
 
 
     }
 }
 

BALL: http://content.screencast.com/users/Loftyy/folders/Jing/media/9edeab36-db0b-4aa5-9b23-e4d0aba67a1f/ball.png

WALL: http://content.screencast.com/users/Loftyy/folders/Jing/media/94a5b966-e9e0-4ad6-8c05-c5af1945d5e0/2015-11-30_0026.png

I hope someone can help me, i'm really determined to fix this and continue on my endeavor.