I had the same problem when I got mine. Only the right image showed up. Stefan told me to play around with the aspect ratio button and that worked. To change the aspect ratio, you have to go to the bottom toolbar at the right and you will see an icon for that. Click and choose "16:9". I don't recall there being an actual "3D" choice so just play around with the choices till you get an image on both sides. You might find this easier by connecting a mouse to the Cinera.
One thing I did notice is that when you choose the aspect ratio, one choice stretches the image right up to the vertical borders. You have to find the one where you get the letterbox format (for movies wider than 16:9) so the entire image appears on the display. It's been a while since I checked this so I forget the exact choices. But I think once you start playing around with the various choices, you'll find the one that works. It's best to use a sample of a letterbox movie or trailer to make sure that the entire width of the clip does display.