Chosen Solution
Today, I replaced the heat sink on my 13 inch mid 2012 MacBook Pro. I had some difficulty getting the keyboard cable in, but in the end I got it all the way. The keyboard worked, or so I thought. Every single key works except the control key. The key seems fine - you can press it like any other key, but nothing happens when you press it. Could I have damaged the cable? I bent it a little bit but it doesn’t look broken at all.
Try the control key on the other side of the keyboard.
Open up the keyboard control panel (Apple Icon > System Prefs > Keyboard) Check off ‘Show keyboard and emoji viewers in menu bar’ Note in the top right you should see a new menu icon click on it and open ‘Show Keyboard Viewer’ Now with the viewer on your screen test the control key does the key viewers icon show you pressing on the key? The Control key doesn’t do much under MacOS so its hard to test.
