We have a UC560 running 8.6.1 and have some 9971's we are testing video calling with. When we make a video call, the video screen comes up, but it is black. In addition, the video camera icon is X'd out.
After researching this, it says check VGA of receiving device (shoudl not matter as they are both 9971's) and in addition to make sure the voice register global has video and camera enabled. I have verified both of these are working ,but we still get the same issue. Both phones are located on the same network as well.