Hmm, I looked at the files, and it’s a very weird problem.
Your materials have the transparency set to 1. Meaning, the converter makes it not visible. However, I have other models lying around with a transparency of 0, that are supposed to be visible too. Now I’m confused. 
To work around, find this part in the resulting .egg file:
<Scalar> blend { add }
<Scalar> blendop-a { one_minus_constant_color }
<Scalar> blendop-b { constant_color }
<Scalar> blendr { 1 }
<Scalar> blendg { 1 }
<Scalar> blendb { 1 }
<Scalar> blenda { 1 }Entirely remove that part.