Can anyone tell me why this code isn't working?

I'm trying to make a simple pong game using a tutorial I found online. The person in the tutorial is using javascript, but i'm trying to follow along using C#.

Here is the script i'm using:

 using UnityEngine;
 using System.Collections;
 
 public class playerScript : MonoBehaviour {
 
     public KeyCode moveUp;
     public KeyCode moveDown;
 
     public float speed = 10f;
 
     // Update is called once per frame
     void Update () 
     {
         Vector2 v = rigidbody2D.velocity;
         if(Input.GetKey(moveUp))
         {
             v.y = speed;
         }
         else if(Input.GetKey (moveDown))
         {
             v.y = speed * -1;
         }
         else
         {
             v.y = 0;
         }
     
     }
 }

I had an issue compiling at first, and had to make my Vector2 into a variable for some reason. I don't know why, but I guess you need a temporary value for rigibody2D.velocity. But the character won't move at all if I hit W or S, which are the keys the public variables are assigned to. Am I missing something due to a c# coding issue?

It seems logical. Two keys created, a speed created. Vector2 v is initialized as the rigidbody's velocity. If I hold w it should move in a positive 10 direction. Reverse for the S key. I'm not understanding the issue.