Scaling dynamic created buttons

Hi,

I'm trying to create a dynamic menu in unity but having a problem where my buttons that i create don't scale correctly. I've put Vertical layout group to my panel but it doesn't trigger.

Here's a picture:

The test buttons are the one i create dynamically, i want it to look like the "Previous" button.

Here's my code where i create the buttons.

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 public class menu : MonoBehaviour {
 
     [SerializeField] GameObject buttonPrefab;
     [SerializeField] Transform menupanel;
 
 
     void Start () {
 
         for (int i = 0; i < 6; i++) {
             GameObject button = (GameObject) Instantiate (buttonPrefab);
             button.GetComponentInChildren<Text>().text = "Test";
             button.transform.localScale = new Vector3 (1.0f, 1.0f, 1.0f);
             button.transform.parent = menupanel;
         }
             
 
     }
         
     
     // Update is called once per frame
     void Update () {
     
     }
 }