No one was happier than I was when Adobe added tethered support in Lightroom for the Canon 5DS last year. However, it seems that after the latest Lightroom update, tethering has once again "broken." The LR dialogue flashes between recognizing the camera and No Camera Detected. When it finally does work, it seems to partially download the one image, but as soon as I take a 2nd image, both the camera and LR lock up...the camera says "Busy" and won't even write to the CF card until I unplug the USB cable. I heavily rely on tethering for my work, and am grateful for any help!!!
Make sure you don’t have any Canon software like EOS Utility also running at the same time.
Make sure you don’t have anything extra plugged into the USB ports, especially not a phone.
Make sure you’re not using a USB Hub, especially one that is unpowered.
Make sure your cables are not too long—test with a short cable attached directly to the computer.
LR talks to a tethering plug-in that talks to a Canon-supplied-library that talks to an OS-supplied USB-driver, so any change or iffyness in any of those can cause a problem.