I have 10 users in my office, and all are setup to allow screen sharing. It works for all of them, except one. On her Mac Pro, we can connect to it with no trouble, but once you see the screen, you cannot control it, even though the "Control" icon (target with cursor) is selected. We have tried toggling between the View mode and the Control mode. We have tried logging in as the user account, and the admin account, with both implicit access, and also by requesting access. In all cases, you can see the screen, but not control it. A couple of times, it seemed as though I could click on a window in the background, and that window would come forward, and then immediately, I would be unable to control it again.
We have tried it with Mojave to Mojave, and Mojave to Catalina. (The target system is on Mojave 14.6.) There are 10 other Macs in the office with the same configuration, and they all work fine.
Any ideas? Thank you!