Problem with 2 face Polygon

Donexer90

Hi all

Have any one came across with 3d print when try to export model to STL or OBJ  and they only show 1 face of Polygon ?

after i use GoZ to export Zbrush i got perfect model like it supost to be but there are part of it only have 1 face poligon at first it let me do everything until i export fix file to printer software they ok to show up but they keep saying error and dont let me slice file 

Can anyone identify the problem and how to fix it ?

Ascania

Well, duh! How do you suppose the printer is gonna print an object with NO THICKNESS?