Resources.LoadAll not working

I'm trying to load a set of prefabs using LoadAll and it won't load my object array (doesn't error at compile time). I'm using version 2017.3.0f3. I've seen this plenty on the forums but can't figure out why mine won't work. I've listed the class in its entirety.

Note that the load of a single prefab GameObject "Thin2" at the end of the Place() function works fine. So I don't think it's my folder structure which is "Resources/Prefabs". I get the first Debug.Log statement fine, then the second errors because Templates is not set to an instance of an object.

 using UnityEngine;
 using UnityEngine.UI;
 
 public class Structures : MonoBehaviour {
 
     private GameObject[] Templates;
     private System.Random random = new System.Random();
 
     public void Start()
     {
         Templates = Resources.LoadAll("Prefabs") as GameObject[];
         Debug.Log("Structures Start Called");
         Debug.Log("Templates count: " + Templates.Length);
     }
 
     public void Place()
     {
         GameObject old = GameObject.FindGameObjectWithTag("structure");
         if (old) { Destroy(old); }
 
         GameObject bullet = GameObject.FindGameObjectWithTag("bullet");
         bullet.GetComponent<Bullet>().ResetHits();
 
         GameObject counter = GameObject.FindGameObjectWithTag("counter");
         counter.GetComponent<Text>().text = "0";
 
         GameObject prefab = (GameObject)Resources.Load("Prefabs/Thin2", typeof(GameObject));
         var structure = (GameObject)Instantiate(prefab, new Vector3(0, 0, 0), Quaternion.identity);
     }
 }