Does right clicking on the Leap Motion Control Panel and selecting "resume tracking" do anything for you?
What AV software are you using? Some users have reported similar issues with certain AV software. Try temporarily disabling/uninstalling your AV software and reinstall the Leap Motion software to see if that helps.
If the issue persists, try installing dpinst64 located in c:\Program Files (x86)\Leap Motion\Core Services\Drivers to see if that helps.
If that doesn't work, please test the controller with another computer to see if there may be an issue with the controller hardware.
Ensure the controller is plugged in directly to your computer and not going through a USB hub as well as that may cause issues.