Why not all keys on a computer keyboard may work
Generally speaking, when the keys on a keyboard don't work, it is due to mechanical failure. When this is the case, the keyboard needs to be replaced. That being said, there are a few cases where nonfunctional keys can be fixed. The following sections explain how to go about this.
Note: This page discusses the steps for troubleshooting a keyboard with some keys that work, not keyboards that have no working keys.
F keys or Number pad keys not working
If the F keys (F1 through F12), or function keys, do not work, check for a F lock key or something similarly named. Pressing this key will activate the F keys and allow you to use them.
If the keys on the Number pad do not work or are behaving oddly (i.e. moving your cursor instead of typing a number), try pressing the Num Lock key. The Num Lock activates the number keys and should type numbers when pressed.
Try multiple programs
Make sure the key is not working in more than one application. Some keys, such as the function keys (F1 through F12), do not work with every program. An easy way to test this is to open Notepad or a word processing program, open your Internet browser, and try the key in both programs.
Reboot and try in Safe Mode
If you are a Microsoft Windows user and specific keys malfunction in all programs, reboot you computer and try the keys in Safe Mode.
Clean the keyboard
Remove the key that isn't working from the keyboard and clean it. In some situations, dirt, hair, dust, and other debris can obstruct keys or cause them to malfunction.
If all of the previous suggestions have been completed and one or more keys are still not working, it is likely that the keyboard is defective and needs to be replaced.