Keyboard Not Working in Mac OS
When trying to use your keyboard on a Macintosh, it does not respond or may only beep, but the mouse still functions.
When you start up with extensions off, the keyboard works again. This is caused by a control panel called Easy Access.
Normally, it is used to assist people with disabilities. However, it can occasionally be activated inadvertently, causing the keyboard to seem like it is no longer working.
To fix this problem, simply go to Control Panels => Easy Access and turn everything off.
Finally, unless there are features you intend to use, it is best to disable Easy Access in the Extensions Manager.