Transparency in certain places of a mesh?

Hi, I need help with a problem in opacity. My imported character it´s supposed to have transparency on the googles but he doesn´t, like I show on the image

I have this similar problem in other character that has a LED behind her face:

And that´s how it should be:

So I know I´m doing something wrong but I have no idea what, what I need to do?
This is the material for both: