Nikon D810 users that have updated to Lightroom 6.1/CC.1 are reporting that Lightroom has lowered the contrast in their images. What’s happened is that profile library file is somehow missing the presence of the Adobe Standard profile. The profile is actually there in the correct location, but it’s hidden to Lightroom.
Lightroom then selects the next available profile, which happens to be Camera Flat, which is a vey low contrast profile, meaning images look pretty horrible.
Adobe have created a knowledge base article explaining a workaround for this Nikon D810 profile issue.