I was helping a family member set up a new computer, a Macbook Pro, and I had them install TeamViewer so I could configure things for them without them having to read everything to me. They got it installed, and I connected, but I couldn’t click on anything on their computer and they couldn’t see me moving the mouse.
I thought this may have been caused by the latest update. When I first tried to connect, I got an error message that their version of TeamViewer was newer than mine and I would have to update before I could connect. I updated to the latest version and then was able to connect successfully, but I could not click on anything or move their mouse. I could see their screen, but that was about it.
It took some digging, but I found the issue was caused by a setting on the new Macbook. Click on the Apple icon in the upper left corner, then choose “System Preferences”. Next, click on the “Security & Privacy” icon in the top row. In the horizontal menu across the top of the window, click on “Privacy”, and then choose “Accessibility” from the vertical menu on the left of the window. You should now see a heading that says “Allow the apps below to control your computer.” If you do not see TeamViewer in the list, click the plus sign below the box to add it. If you do see TeamViewer in the list, make sure the box next to it is checked so that TeamViewer has permission to control your computer.
This fixed it for me instantly, but you may need to close and reopen TeamViewer before the changes take effect.