I am curious what you have in your bag of tricks for debugging 3d graphics. I know it is a broad question, but I'm hoping there are some really good ideas out there floating around in the ether that I haven't stumbled upon yet.
I see this with beginners a lot. Most of the problems in a beginning OpenGL class were students putting everything into the scene, and then nothing shows up. To me, it is a "black screen of death". Where is my model? There aren't any errors, and no way to really figure out what's wrong. But that feels like guessing, and debugging by guessing never works out.
For example, when I was writing a software renderer from scratch, I was trying to clip in homogeneous coordinates. But I didn't really understand the math, so when I tried out the clip code I got an array index out of bound exception (this was in Java). Well great. I had no idea how to fix that. I ended up setting up four views: top, left, front, and perspective, and then drawing the view frustum, hand clipping all the lines so nothing would crash. Then I could see what was happening. It ended up being a sign error in the near clipping plane. It was easy to fix, but it took two weeks of side work to find it.
What do you do when you load up a scene and nothing is there?