Q: camera does not show up in finder

does image capture see it ?

Open Image Capture and set the import feature to Lightroom.

It's much easier and more  trouble free to remove the SD card from the camera and use either iMacs card reader or get an external card reader to download your photos to Lightroom.

Besides all the suggestions you have been given, repair permissions and restart your computer if you do not have El Capitan.  If you do have El Capitan, just restart.

Zapping your pram usually resolves usb issues.

Make sure your camera is in Mass Storage, and remember you can also import from your camera directly to LR, and directly to external disks for storage. Check the LR manual for more.