porksmash

I have a black image on a transparent background. I'm trying to import it into a laser engraving program that claims it supports PNGs, but it fails. This program is fairly new to me, so I'm still not sure of its capabilities (and it didn't come with any help). I am taking a wild guess here that it is expecting something closer to a black and white image. So basically, is it possible to save a PNG with less than 8-bit depth?