Jump not working?

I've recently started to make a 2D platformer game. I got the character to move around by using the A and D keys, but then when I started to follow some tutorials on how to make the character jump, none of them would work! Here is the code for my current jump program.

Code (CSharp):

1. using System.Collections;
2. using System.Collections.Generic;
3. using UnityEngine;
4.  
5. public class JumpingScript : MonoBehaviour
6. {
7.     public float fallMultiplier = 2.5f;
8.     public float lowJumpMultiplier = 2f;
9.  
10.     Rigidbody2D rb;
11.  
12.     void Awake()
13.     {
14.         rb = GetComponent<Rigidbody2D>();
15.     }
16.  
17.     void Update()
18.     {
19.         if (rb.velocity.y < 0)
20.         {
21.             rb.velocity += Vector2.up * Physics2D.gravity.y * (fallMultiplier - 1) * Time.deltaTime;
22.         } else if(rb.velocity.y > 0 && !Input.GetKeyDown(KeyCode.UpArrow))
23.         {
24.             rb.velocity += Vector2.up * Physics2D.gravity.y * (lowJumpMultiplier - 1) * Time.deltaTime;
25.             Debug.Log("it works!");
26.         }
27.     }
28. }
29.  

I made the key to jump the up arrow and even made a debug log tester. The tester worked, so whenever I pressed the up arrow it would say "it works!" in the console, but my character would not jump. Any help is greatly appreciated!

 

This video is great for newbies. It will give you a foundation to build off of.

 

Thank you so much!