For anyone who dragged the Sprite Sheet into the Tile Palette only to see nothing happen, this appears to be a known bug in certain versions of 2017 and 2018:
https://forum.unity.com/threads/tile-palette.529314/
This was using Unity 2018.1.1f1. Reverting to 2017.4.4f1 fixed it.
It was fixed in the newest Unity update.
Thanks for the information. It depends on what is mean by the newest update. The linked thread mentioned it was fixed in the 2018 beta branch, but I did not confirm that. I had an install issue with the latest stable 2018.1.21f, so I was not able to confirm that one.
It is working in 2017.4.4f1 as well.
It didn’t show in Unity 2018.1.1f1 for me either. I downgraded to Unity 2017.4.1ff and it worked. There is a discussion on the Unity forum about this: https://forum.unity.com/threads/tile-palette.529314/
Neverminddddd