I have seen dozens of posts for different operating systems, camera models, and configurations though I have not found a single workable solution from Canon experts or the community.
I've been using my EOS 6D (mk 1) for Zoom calls for a little over a month and, other than issues of stutter in the feed (yes, I know, expected when using USB 2.0 to send even 640 30fps) it was working pretty well and the overall image quality and DoF was a welcome improvement despite the bandwidth issues. I was delighted to see Canon get with the times and offer a solution that didn't require a $200 streamer "hockey puck" to compress and make stream ready HD video from my DSLR. At any rate, about a month in, EOS Utility 3 and/or webcam utility (both latest versions for the 6D) just decided "we're not going to recognize your camera anymore" and I've been stuck with the greyed out screen in EOS Utility 3 with no way to access liveview shooting or access data on the camera. No, wifi is not on. I've tried it with the camera set to video AND photo mode. I've been able to remote capture in Adobe Lightroom Classic (although, it doesn't seem like liveview was working there, either). I can see my 6D as a USB device in system report AND I can see it as a device in Image Capture. I have unistalled and reinstalled both Webcam Utility and EOS Utility probably on the order of twenty times. This morning, as I neared the point where I just light my Canon gear on fire in my yard, I tested on my MacBook Pro and what do you know, EOS Utility 3 AND liveview WORK FINE. Either there are some settings or prefs buried in the Library folder that are not removed when clicking and dragging utility apps to the trash on a Mac (only webcam utility seems to have an unistall packaged with the software) or this stuff is so unstable that it works, then doesn't but then works fine on Macs with earlier OSs (MacBook pro OS is 10.15.4)
Calling Canon on the 6D traps you in an endless loop of "this camera is only supported online"
Anyone out there in the community have a fix because it's clear at this point Canon does not.
Are you saying that it used to work, and now it does not? If so, then something has apparently changed. What do you think has changed to make it suddenly not work, anymore? My guess is an OS update from Apple.