I'm using windows 7, trying to download pictures from my canon 5d mark 2, but when I click import, the camera does not appear. I've tried changing USB ports, switching the camera on and off, trying a different USB cord, tried a different camera, but nothing. Please help! This problem only started a few days ago on lightroom 3.6, upgraded to 5.5, but still not working. Thanks.
Can you see the Canon EOS camera and image files using Windows Explorer? If not disconnect the camera, close all applications' shutdown Windows, and TURN OFF the power to your system and ALL connected devices. Disconnect all phones, iPads, and any other USB devices and restart your system.
Retry Windows Explorer and see if your camera is showing. If so try LR import again.