Photoshop - Clipping Mask not Working

A typical mockup template will have smart object layers on top of the layer stack that you edit or replace content to populate the template makes  the mockup easy to use and easy to batch populated with Photoshop scripting.  The  top smart object layers may not be visible in the mockup.  Their main function is to make the mockup template easy to use. 

A typical mockup template may look something like this one.  While my scripts can populate it.  They can not adjust  the overlay layer for shadows, highlight and textures.  I don't know how to code AI type code I don't have that  intelligence myself to make the adjustment right for the changed content. 

There are several ways to do this, here is one way:

Go to layers panel, click the four little lines and duplicate the layer. Then go to you selection tool in the tools panel on the left of the screen. Click all the area inside the t-shirt hold down the shift key while doing the selections. Then create a new layer, in the layer panel. Go back to tools on the left again and make sure black color is selected and click on the paint bucket toolin the tools panel. Then click inside your highlighted area that should fill the entire shirt black. Then click the new layer and the filled layer and go to layer merge. The you can select the entire shirt and click select, select and mask.

Hai @defaultpvh8ml5eb2za, i see your T Shirt Front just an outline image. Maybe you can fill first the t-shirt and than you can fill with the color 😄 

Can anyone shed any light on how to fix this?