The button has a layer in it that has a bevel/emboss filter on it. I'm stumped.
Changed the fill of the shape to 0 and added a copy to mask the background. Saved it as a PNG with transparency like this:
(The button text is transparent, you will see it if you view the image on a black background)
The first 2 steps will make your button shape "see-through." After playing around with Bevel and Emboss, adding a soft drop shadow and inner glow, I get something like this: