Why does my inventory show '0 in stock' vs 'not tracked' on Printful?

[lupeandpono]

I am including a picture from my products list to show what I mean.

I am working on adding shirts right now, so this is the same product with a different design on each.  I may alter the colors of shirts I chose but I don't see a correlation between this happening when I chose certain colors so it seems to be more an issue with how I LIST the product rather than the actual product.  

What I don't understand is how I am doing it on some but not all.  I am using the Printful app in shopify and everything is going in so seamlessly, but I have these occasional ones which list as 0 in stock with (however many) variants. 

My problem is that sometimes the 0 in stock ones don't seem to connect to printful and therefore the order needs to be entered manually.  I am missing some of these and have to go back and enter them trough printful when I realize an order took place but nothing happened.  The ones listed as inventory not tracked have no problem being streamlined and the orders go out as they should.

So what am I doing wrong sometimes?