Issue with tower defense tutorial

[dim salmon]

I think this is an easy fix, but I was following Brackeys tower defense series and I wanted my turrets to have 3 tiers (levels).

I tried to make it so that when a turret becomes tier 2, it makes the button that upgrades to tier 3 interactable, but it's not working for me.

This is my code:
Also "junk" is my currency

if (!target.isTier2)
{
upgradeButtonTier3.enabled = false;

      Tier2upgradeCost.text = target.TurretBlueprint.Tier2upgradeCost + "junk";
      upgradeButtonTier2.interactable = true;
    } else
    {
        Tier2upgradeCost.text = "MAX";
        upgradeButtonTier2.interactable = false;
        **upgradeButtonTier3.interactable = true;**
    }