Setting the parent of a transform which resides in a prefab is disabled to prevent data corruption. Even though editing through instance, not prefab.

That should just be Instantiate(prefabGO)or (GameObject)Instantiate(prefabGO) if you prefer.

If that doesn't fix it: Can we see more of your code, and are you doing this at runtime or in an editor script?

That didn't work. The issue is that it seems to think that i'm trying to work with the prefab rather than an instance. Either that or i'm making a mistake elsewhere.

Here's all the code from the function i'm working on

  public void loadECTUnlockables()
     {
         if (!unlockablesLoaded)
         {
             unlockablesLoaded = true;
             foreach(Unlockable uable in Resources.LoadAll<Unlockable>("Unlockables/EnemyCellTypeUnlockables/"))
             {
                 print(Resources.LoadAll<Unlockable>("Unlockables/EnemyCellTypeUnlockables/").Length);
                 uable.cellIconUI.sprite = uable.uIcon;
                 
                 if(!uable.isUnlocked())
                 {
                     uable.cellLockedUI.enabled = true;
                     uable.cellToggleUI.gameObject.SetActive(false);
                 }
                 else
                 {
                     int ii = 0;
                     foreach (string text in uable.cellEffectList)
                     {
                         GameObject tempText = (GameObject)Instantiate(textObject);
                         tempText.transform.SetParent(uable.cellEffectListUI.transform);
                         tempText.GetComponent<Text>().text = uable.cellEffectList[ii];
 
                         ii++;
                     }
                 }
 
                 GameObject tempUable = Instantiate<GameObject>(uable.gameObject);
                 tempUable.transform.SetParent(cellTypeList);
             }
         }
     }