There is no tethered support for the 5D in any version of LR. Only the 5Dii and 5Diii are supported
You could try the EOS utility disk that came with the camera.
If you are using a Mac you can use Image Capture to tether the 5D classic and then use a Watched Folder in Lightroom to automatically import them. It was working for me a few months ago so hopefully any Apple upgrades didn't break it. (Apple has broken all kinds of things lately,Adobe too)