Do you have any other idea that can help?
The easiest method is to take the SD card out of the camera and stick it in the SD slot in your computer, or if you don't have a computer equipped with such a slot, into the SD slot of a memory card reader. Cheap readers cost as little as $5; better ones read faster, work with more kinds of cards, and cost maybe $20.
Another option is to transfer the images via the 6D's built-in WiFi. If you've never done this before you'll probably have to spend a few minutes with the manual to get things configured right, but after that the only drawbacks are that it uses (relatively) a lot of battery power and isn't nearly as fast as reading the images straight from the card.
the only thing i can think about is that the cable is damaged (while connecting to the computer any lights turn on the camera?)
Whether connecting via USB or WiFi, the camera will need to be switched on in order to be recognized, so the back display may be active. Also, there's a red "access lamp" on the back of the camera that lights when reading the memory card, and you'll see that light up as you start to read images from the camera.