video feed is one-way only

When screen sharing, we find that the person helping can see video feed of the person helped, but not vice versa. The helped person sees the black video box but no camera icon to enable. Is this normal? Is there a fix I'm missing?

Screen viewing and remote control works perfectly. All connections are started as remote control. It's only video (IOW faces) that fails, and only in one direction. Audio worked at all times.

I think we are following the instructions given in the first reply here:

https://community.teamviewer.com/t5/General-Questions/How-to-use-video-call-and-remote-control-at-the-same-time/m-p/10985

Details: I've used TV before but not with video feed. Now friend D is trying to help friend J, having never used TV before, and I'm acting as advisor. D thinks communication with J (who is the least techie of us) will be much better with video feed -- just different personalities.

I'm on Windows 7. D and J are both on the latest Mac OS X. I updated TV to the latest version last week, at the same time D installed it. J installed TV a couple of days later.

But the syndrome is the same whether it's Win<->Mac or Mac<->Mac. At the moment I don't have a way to test Win<->Win.

First attempt, I acted as helper with D as helped (so that D would understand what J would later see). D turned on video feed and I could see her for the rest of the call. D and I both saw a black box where my face should be, and I saw nothing to activate it.

Second attempt, D and I reversed roles. I saw the camera/slash icon, clicked it, and D and I both saw my face in the video box. (Thus it was not a matter of my camera being disabled.) D saw no way to enable video of her face, just the black box with no icon.

Later D tried with J, both directions, with the same results.

So as at the top ... is this normal, and if not, can I fix it?