Make sure you are connect to a powered USB port directly on your computer, not a USB port on a keyboard or USB hub.
Disconnect the Lytro camera from your computer, at both ends of the USB cable.
Shut down the Lytro Desktop application fully (Mac: Lytro -> "Quit" or "Command"+"Q", Windows: use the red "x" in the upper right of the window).
Check to make sure there are new pictures on your camera; to be sure all pictures were not previously imported, please take a couple of test pictures. (Right now re-importing pictures is not supported.)
Reset the camera: swipe up on the touchscreen to access the General Control Drawer, then touch the "gear" icon and select "Reset."
Re-launch the Lytro Desktop application on your computer.
Reconnect the USB cable firmly at both ends.
IMPORTANT: Still having trouble? Please use the blue "Open a Support Ticket" link below to open a Support ticket.