If the Leap Motion software does not appear to be producing data, stop the Leap Motion service or daemon and restart it. Unplug the Leap Motion device and plug it back in.
On Windows to start/stop the Leap service, run the following commands in the console in Administrator mode:
net stop LeapService
net start LeapService
On Mac, run the following commands:
sudo launchctl unload /Library/LaunchDaemons/com.leapmotion.leapd.plist
sudo launchctl load /Library/LaunchDaemons/com.leapmotion.leapd.plist
On Linux, leapd is still a user process.
To stop, press Ctrl+C if you are running interactively. If running in the background, use ps -A to find its process ID before terminating with the kill command.
To restart, just run leapd again.