AssetPreview.GetAssetPreview always returns null.

Hey All

I'm working in Unity 5.5 and am trying to use AssetPreview.GetAssetPreview to retrieve thumbnails of my prefab objects that can be used in a menu.
I know that AssetPreview.GetAssetPreview works asynchronously so I added the loop but it constantly gets stuck in a infinite loop. Never returning any of the Texture2Ds.

Code (CSharp):

1. void GetThumbnails()
2. {
3.         Object[] myPrefabs = Resources.LoadAll("Prefabs");
4.  
5.         AssetPreview.SetPreviewTextureCacheSize(myPrefabs.Length);
6.  
7.         for(int i = 0; i < myPrefabs.Length; ++i)
8.         {
9.             Texture2D ThumbnailTexture = AssetPreview.GetAssetPreview(myPrefabs[i]);
10.  
11.             bool breakout = false;
12.  
13.             while (AssetPreview.IsLoadingAssetPreview(myPrefabs[i].GetInstanceID()))
14.             {
15.                 Debug.Log("Loading Asset Preview");
16.                 if (breakout)
17.                     break;
18.             }
19.             Sprite tempSprite = Sprite.Create(ThumbnailTexture, new Rect(0, 0, ThumbnailTexture.width,                                                                                  ThumbnailTexture.height), new Vector2(0, 0), 100);
20.             ThumbnailImages.Add(tempSprite);
21. }

P.S. Breakout is in there so when I'm debugging I don't have to Crtl-S***-Esc unity everytime it gets stuck in a loop.