Add Force not working

I have a first person character which i want to make jump. I have a rigidbody and a character controller attached. The rigidbody is set to: Enable gravity - true, is keinematic - false and restrict x and z movement and all rotation. This is my code.

 [RequireComponent(typeof(CharacterController))]
 [RequireComponent(typeof(Rigidbody))]
 public class playerMove : MonoBehaviour {
     public float speed = 60.0F;
     public float sideSpeed = 40.0F;
     public float jumpForce = 80.0F;
     public float sensitivity = 30.0F;
     public float gravity = 20.0F;
 
     void Update() {
         Rigidbody rb = GetComponent<Rigidbody> ();
         CharacterController controller = GetComponent<CharacterController> ();
 
         Vector3 forward = transform.TransformDirection (Vector3.forward);
         Vector3 sideways = transform.TransformDirection (Vector3.right);
         Vector3 up = transform.up;
 
         float curSpeed = speed * Input.GetAxis ("Vertical") * Time.deltaTime;
         float curSideSpeed = sideSpeed * Input.GetAxis ("Horizontal") * Time.deltaTime;
         float rotation = Input.GetAxis ("Mouse X") * sensitivity * Time.deltaTime;
 
         controller.SimpleMove (forward * curSpeed);
         controller.SimpleMove (sideways * curSideSpeed);
         transform.Rotate (0, rotation, 0);
 
         if (Input.GetKeyDown(KeyCode.Space) && controller.isGrounded) {
             rb.AddForce(up * jumpForce);
             Debug.Log ("Adding Force");
         }
     }
 }

Any ideas why this is happening?