I have all of the latest updates for both lightroom and photoshop. When I select more than one image and choose the option to "Open as Layers in Photoshop", lightroom hangs and then I get an error that says it can't open photoshop. I've used this a lot with other backs (40D, 7D mark ii).
Is this a known bug due to the 5d mark iv being new? My work around is to open the images individually in photoshop and then combine them.
There's a known bug in Lightroom regarding this. I have the same problems with files from a Canon 6D and 70D
Just open PS first and that option works.