Note that a material that usesThe SpriteRenderer component automatically replaces the "Sprite Lit Default" shader does not have a slot for a basediffuse/base texture. It only has slots for "Diffuse", "Mask" and "Normal" textures. That's because of the base texturematerial that is taken fromassigned to it with the "Sprite"Sprite asset assigned to the "SpriteRenderer" componentSpriteRenderer. When you don't have a sprite assigned, then it uses the plain white placeholder sprite instead.
Which means you need to assign the JPG with the base texture to the Sprite of the SpriteRenderer. You can then use the properties of the material for additional special effects like normal mapping.