material show black in ipad

when I use gl draw a texture,It shows black in ipad,but it shows well in pc. Then I drag this material to a cube gameobject,the cube's materail shows well in pc and ipad.Anyone can tell me how to show this material on ipad use gl,thanks! the gl code is following:

 doorMaterail.SetPass(3); 
 GL.Begin (GL.QUADS);
 GL.Vertex(DrawRoom.door.ThreeDPoints[0]);
 GL.TexCoord2(0,0);
 GL.Vertex(DrawRoom.door.ThreeDPoints[1]);
 GL.TexCoord2(0,1);
 GL.Vertex(DrawRoom.door.ThreeDPoints[2]);
 GL.TexCoord2(1,1);
 GL.Vertex(DrawRoom.door.ThreeDPoints[3]);
 GL.TexCoord2(1,0);
 GL.End ();