I've used Lightroom for years and never had any problems tethering my camera until now. I'm running the latest versions of all Adobe apps, OS (Mojave 10.14.1) and camera firmware. I've tried all the usual troubleshooting tips - restarting, reinstalling, etc. If I use another tethering app, it works fine so something's broken on the Adobe compatibility side.
Now the tethering works intermittently - sometimes it'll connect and be fine, and then 30 mins into the shoot the camera will stop being detected. I restart, and maybe it'll start working again, maybe it won't. There's no pattern and I can't determine exactly when it stopped working as I only use tethered shooting once or twice a month, so I can't link it to any specific update.
This Crash Report dialog shows up now which must be the problem.
Sorry to hear that Lightroom crashed on tethering the Nikon camera, could you please try all the steps mentioned on this article and let us know if it helps?