I've had this problem before too, but I don't remember what the settings of my scene were. In new scenes I can make the mia materials show in renders right away.
Does it show in the viewport? Have you pressed 6 on the keyboard?
Edit:
Make sure your render is set to Mental Ray. It is on default on Maya Software, and it cannot see Mia Materials.
Also try to re-load Mayatomr.mll, maybe it's a bug if you already tried MentalRay rendering with default / production settings.
the color changes in the viewport when I apply the material but it doesnt show up in rendering at all. Mental ray won't work. Blinns and lamberts etc seem fine
Last edited by jarwulf; 09-05-2013 at 07:00 AM.