Not all keys on keyboard work
Generally speaking, when the keys on a keyboard don't work it is due to mechanical failure. When this is the case, they keyboard will need to be replaced. That being said, there are a few choice instances in which nonfunctional keys can be fixed; the following sections explain how to go about it. It should be noted that this document is for troubleshooting a keyboard with some functioning keys, not keyboards that have no working keys at all.
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 other word processing program along with your Internet browser and try the key in both.
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 keyboard 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 your keyboard still is not working, it is likely that the keyboard is defective and needs to be replaced.