We don't see Canon EOS 0D listed in the list supported cameras in Lightroom, refer: A list of cameras that can be tethered to Lightroom.
Please refer the below troubleshooting articles for fixing the tether shoot ,also the known issues in Lightroom CC 2015.8/6.8.
I'm having an identical problem to that described above, as follows:
"After I fill in the fields, and click OK, the operating bar opens, showing the camera, along with a place for shutter speed, F-Stop, and ISO. Also displayed is a large button to release the shutter. However, none of these indicators show the corresponding values, and the shutter button doesn’t release the shutter." Only difference for me is that I'm using Lightroom 3 and a Canon Rebel XT, and Mac OSX Yosemite V. 10.10.5. According to the link, this combination of camera and version of Lightroom should be compatible. And I do have the communication set to "PC connection" which I've seen on other forums can cause a problem when not set to this.
Have you tried creating a new catalog in Lightroom 3 and check if that helps? Also, please let us know the exact version of Lightroom you are using now? You can check that by going to Lightroom > help menu > system info.
Also, check if there are any pending updates for Lightroom 3?
Lightroom Version 3.2, Camera Raw 6.2. The most current version of Lightroom is 3.6. I don’t see a way to upgrade from 3.2 to 3.6 on the Adobe website, and it’s my understanding that the most current version of Lightroom won’t allow tethering with my now-older Canon Rebel XT, which is why I bought a used copy of Lightroom 3.
When I open Lightroom and then turn my camera on, the camera does show up as a Source, and I can then snap a photo, use Copy as DNG, and import it. The photo does then show up in Library and can be Developed. So the program is able to “work with” the camera, which is why the tethering issue is odd to me. From the Library module I then go to File>Tethered Capture>Start Tethered Capture…>OK (using the default settings). This is the point that the bar appears with my camera listed as a source, but with none of the camera’s settings listed, and it is essentially nonfunctional. The image of the shutter release button responds when I click the cursor over it, but nothing happens.
If I open a new catalog, I have to then turn the camera off and back on again to get Lightroom to recognize it, then I’m back to square one and the cycle I described above repeats itself.
Thanks Mohit, for the feedback.