Why won't my ball jump?

public class Move : MonoBehaviour {

    private Rigidbody rb;
    public float speed = 10;
    public bool jump = false;
    public float jumpUp = 0;

	// Use this for initialization 	void Start () {
        rb = GetComponent<Rigidbody>(); 	} 	 	// Update is called once per frame 	void Update () { 	 	}

    // Update is called once per physics calculations
    void FixedUpdate()
    {
        float moveHorizontal = Input.GetAxis("Mouse X");
        float moveVertical = Input.GetAxis("Mouse Y");
        jump = Input.GetButtonDown("space");

        if (jump == true)
        {
            jumpUp = 10.0f;
        }

        Vector3 movement = new Vector3(moveHorizontal * speed, jumpUp
* speed, moveVertical * speed);

        jump = false;    

        rb.AddForce(movement);
    } }

AddForce assumes ForceMode.Force if you don’t specify it. That is designed for continuous forces. It should work if you split this code:

Vector3 movement = new Vector3(moveHorizontal * speed, 0f, moveVertical * speed);
Vector3 jumpForce = new Vector3(0f, jump, 0f);

rb.AddForce(movement);
rb.AddForce(jumpForce, ForceMode.Impulse);