Fix for 789uiojkl keys or numeric keypad not working

If typing 789uiojkl or the numeric keypad on your keyboard are not producing any output on your screen, it usually indicates that you somehow have the Mouse Keys feature activated.  Often there is no way to explain how this might have happened.  

Into order to turn it off on a Mac, you need to go to System Settings > Accessibility > Pointer Control > Alternative Control Methods and uncheck the box for Enable Mouse Keys.  Also click on ⓘ or Options and make sure the box for "Press Option key five times to toggle Mouse Keys" is unchecked.

Also make sure Mouse Keys is turned OFF in System Settings > Lock Screen > Accessibility Options

If you think you are locked out of your machine because Mouse Keys is on and you cannot enter your password, try connecting a full keyboard with numpad. Mouse Keys should normally only affect the numpad and all the keys on the rest of the keyboard should function normally.

If you have this problem on an iPad or iPhone, the place to turn off Mouse Keys is Settings > Accessibility > Touch > Assistive Touch.