*Updated 12/11/2016 - Adobe released Lightroom CC 2015.8 this week which includes support for tethered shooting with the 5DMarkII.
Trying to get your new Canon 5D Mark IV to talk to Lightroom with a USB 3.0 connection? Tried everything? Been Googling the interwebs for the past two hours trying to find a solution? If you're reading this, you are probably so frustrated that you want to punch a baby. Take a deep breath and let's see if we can work through it . . .
First off, let me tell you about the system I'm using, I'm on a MacBook Pro (retina) with OS 10.12.1 Sierra using the Canon 5D Mark IV. I have the camera connected via USB 3.0 to Adobe Lightroom CC 2015.7 (the latest version as of the date of this post, and the first version to have camera support for the 5D Mark IV).
I can start a new tether session in Lightroom, and Lightroom sees my camera. But when I try and fire the shutter, nothing happens. There's also an icon of a computer on the LCD of the camera (any of this sounding familiar?)
I tested with Capture One Pro 9.3 and everything works as it should . . . and it's fast. Really really fast. I mean the first few frames we were wondering what was taking so long for the images to transfer, only to find out they were transferring so fast we were missing it!
This is all happening without any tether boosters or powered hubs, it seems Canon may have finally gotten their USB 3.0 under control. Yay! (I hate extra cables and parts dangling from my camera).
This is going to sound nuts, but I spent a bunch of time combing through the Google machine looking for answers. This was the most logical thing I could find, so I gave it a shot. Low and behold, it works! It's still kinda nuts though. The solution I found was split between several sources, so I figured it out and decided to create one tidy little tutorial here to make it easy on you.