(Custom resource pack) Dirt not showing up on grass block

Im making a custom resource pack, and am almost ready to publish early access, but there is a major problem—the grass blocks are not displaying the custom dirt that I have made. It shows the custom grass—The top of the block—but not the dirt. 

Im not sure whats wrong, I've changed everything that's related the dirt and grass, but it will not show up! There are some screenshots below detailing the problem.

I really need some help. Im not sure if my problem falls under the 'bugs' category, but Im not sure where else I would go too. Im following the tutorial on MC wiki properly but nothing is adding up. I cannot find anything online—the internet—so Im turning here.