Apple has clearly put its FaceTime video service as a top priority feature for support at present, to ensure that all of us can maintain contact with our loved ones and colleagues while we’re locked down. For that, I for one am very grateful.
If you’re having problems with FaceTime video, I urge you to report them to Apple Support so that any remaining bugs can be sorted out. Note that hardware and software requirements for Group FaceTime are quite stringent, and detailed here. But regular FaceTime connections should be more accommodating.
Ronald, for example, has just had problems activating FaceTime video in Messages on iOS devices running iOS 12.4.6. He’s reported those to Apple, and we hope that they’ll be fixed as a matter of urgency. I’m grateful to him for drawing attention to this issue.
If you don’t tell Apple of a problem with FaceTime or Messages, then it isn’t likely to get fixed. And you never know, Apple Support may already have a solution to help you.