I use my D810 with Lightroom 5.7 for tethered shootings, both with laptops on Windows 7 and on Windows 8.1.
No trouble with windows 7 professionnal, but with Windows 8.1 Lightroom doesn't recognize the camera half of the time.
When it's OK, the green back LED on the D810 body blinks for 1'20'' to 1'30'' before the connection. When something's wrong, the green LED doesn't blink and Lightroom doesn't recognize the camera.
I checked the update of the USB drivers and installed the D810 firmware update.
Already checked these sources :
Someone tried to install the config.lua.zip on LR5.7 (released for LR5.2/5.3) ? Any other idea ?
Maybe a too long USB cable? Using the USB cable current can heat it up and resistance may grow, so if its lengh is about 5m long, it is on the border of working and not working.
If You are in a colder environment (couple of degree may be enough) You may have better experience.
You did not wrote more about the difference between the two cases, just the OP systems.