What do you mean by not showing up? Is the model black when you open it up?. If that is the case you have textures that are in a differant format, more than likely PCX. If that is the case simply resaveing them as bmp, will fix the problem.
Case in point The ISC ships from Ghost fleet dock 13's web site were that way, The ship showed up but the textures would not, because the textures got saved in a format the game or Max did not reconise for some reason, and simply opening up photoshop or painshop pro and resaveing them in bmp format fixed the peroblem.
If you dont have Photoshop or Paint shop pro send the ship and all my way And ill fix it.