Same on 6.9.21027.6898
Ran into this today - solution for me was simpler than above, just requiring the screen connect to be added to the security * privacy tab. System Preferences > Security & Privacy >Privacy > AccessibilitySearch for the Screen Connect app from the search window and click Open
Check it's added to the list of apps
As I had view access - I managed to get this done by a remote user, and as soon as it was done I had full control again. No need for reboots etc..
Customer support service by UserEcho