Please make sure the model can actually be seen in the view of the camera. Also there should be a light present.
Maybe double-check the filename in the object properties too. You can use the expression modelProgress to see if it returns 100 at any point.
Another thing could be the scale of the model, which depending on how you created/exported it might be very small or gigantic.
If everything fails feel free to contact me directly and I will take a look at it.
Oh and again: make sure that it's not simply a case of Construct 2 layers being visible and covering everything up. The 3D canvas is behind the C2 canvas, therefore C2 layers need to be invisible (if not transparent).