I can't get my D300 to tether on Windows 10 with 2015.4. It works fine on 5.7.
I asked for people on a different forum to try tethering their Nikons with that version of LR and Win 10, and nobody had any trouble. It's a mystery. Adobe has a web page that lists things to try. None of them helped me, but they might help you.
I have been through that page, again nothing. As described, it was working with a slight detection lag....but now nothing, and for no reason it would appear.
Anyone from adobe float these forums?