Jumping in Unity C#

So, I want my player (currently just a box), to jump.
Here’s the code I tried:

using UnityEngine;
using System.Collections;
using System.Collections.Generic;

public class jump : MonoBehaviour {
    public float jumpSpd = 5f;
    public Rigidbody rb;
    private float isPrintDone = 0;
    void Start ()
    {
        rb = GetComponent<Rigidbody>();
	}

    void Jump()
    {
        rb.AddForce(0, 8, 0);
    }
	void Update ()
    {
        if (Input.GetKeyDown (KeyCode.F))
        {
            Jump();
            if(isPrintDone > 0)
            {
                isPrintDone += 1;
                print("Jump Called");
            }
        }
	}
}

and in the console I don’t get “Jump Called”, and my player’s acceleration doesn’t change at all. Help? (Also I’m really bad at asking questions, please ask for specification if needed.) I’ve determined that it’s a problem with calling if I press the letter F, not the jump code itself.

rigidbody.AddForce(Vector3.up * jumpSpd, ForceMode.Force);

Doesn’t work either.

rigidbody2D.AddForce(Vector2.up * jumpSpeed, ForceMode2D.Force);
Try this

@Dennisdb1997 when changing vector2 to vector3, and remove all 2d’s (It’s a 3d game), it doesn’t work. I think it doesn’t recognize me pressing F