Text isn't showing up on button

In my clicker game I have a set of code:

 using UnityEngine;
 using System.Collections;
 
 public class UpgradeManager : MonoBehaviour {

     public Click click;
 
     public UnityEngine.UI.Text itemInfo;
 
     public float cost;
 
     public int count = 0;
 
     public int clickPower;
 
     public string itemName;
 
     private float _newCost;
 
 
     void update () {
 
         itemInfo.text = itemName + "\nCost: " + cost + "\nMPC: +" + clickPower;

 //MPC is the "power" of the item
 
     }

This code is supposed to display the item name, the cost and the "power" of it. However, when I play the game, the buttons do not show the text. If anyone know why this is happening, I would really like to know. Thanks!