By the looks of your atlas, I’m assuming that this is for a 2D scene. You shouldn’t use material editor or texcoord for sprites. You have to follow the Paper2D system workflow meaning that When you import your 2D atlas to create individual sprites.
In the sprites’ settings you would be able to specify the location of your tile in the source atlas/texture.
you can do this by simply right click on the texture file in content browser> Sprite Actions>Create Sprite then double click your sprite to change settings.