Seamless Pixilated Terrain Grass Texture. 

how to fix pink texture for now, until S&Box devs fix it. 
1. You need to download each of this texture
2 rename it in order. GrassAlbedo GrassAO GrassHeight GrassNormal GrassRough
3. Then drop it to  Assets/scene/terrain/textures/grass/
4. Then add the material to terrain again or update it and it will work.