If you are on a Mac using El Capitan, tethering is not supported for Nikon and Canon cameras at the present time.
Any ideas on time frame till fix
No. I don't work for Adobe. But anyone who works for Adobe is under nondisclosure agreements. It will be fixed when it is fixed.
Adobe uses a Nikon software component for tethering and Nikon hasn’t released a fix yet, even for tethering with their own camera remote-control products so the ball is in Nikon’s court.
Keep an eye on this Nikon SDK page, that lists when it’s been updated, then assume Adobe will incorporate the fix in the next version of Lightroom after that.
Here is the Nikon SDK page, which shows the most recent update was in July 2015:
It’s conceivable that Apple might change something in an El Capitan update to make things work, as well, but don’t hold your breath.