I just bought a refurb D810 from Cameta with 72 clicks...upgrade from my awesome D7000. The first lens I put on the D810 was my Nikon 24-70mm. Auto-focus was working so I know there was connectivity, however when I took a picture, it was black. I took off the 24-70mm and put on my Nikon 70-200mm. Worked just fine. To be sure, I put the 24-70mm back on the D7000 and it took pics no problem.
So I put the 24-70mm back on the D810 and the only thing I did was cycle the M/A - A button and take a picture with the flash...then it worked. I also took a pic without the flash and the lens worked. What I don't know is why the 24-70mm lens didn't take a pic initially. I don't know whether to suspect the camera or the lens...because each works fine when using another lens or on the D7000, respectively. Just curious if it's just some noob D810 user issue I overlooked. I'll need to interchange lenses again to see if I can replicate the issue and also put on my 50mm to see if there situation replicates with that lens. But thought I'd poll the seasoned Nikon users here. Thanks in advance for sharing your knowledge.