D800 E will not mount on Macbook Pro

I know my D700 does not function as a card reader type device, so it's not gonna show up in Finder or on your desktop as a disk. You have to use the Image Capture application to view and transfer the images from the camera. I would assume your D800 works the same way. This isn't an Apple problem, the camera simply doesn't function as a USB Mass Storage device.

In my experience, a dedicated USB card reader is faster and more reliable than transferring directly from the camera. Your new MBP supports USB 3, so you should go shopping for a USB 3 card reader for the best speed.

Hope that helps.