Hi Arun,

For various reasons, keyboards on both laptops and desktops may suddenly stop functioning properly. This is not a common problem, but when it happens, either some or all keys stop working (depending on the situation), or features of the keyboard such as backlighting may not work.

Please follow below steps to resolve this issue.

1. Check for Crumbs
If you have a keyboard vacuum or a can of compressed air, give the nooks and crannies of your keyboard a quick cleaning. Hold your laptop upside down or at the very least at a 45- to 75-degree angle from horizontal and give the laptop a good shake.

2. Reboot laptop
If you can't use the trackpad or mouse to reboot the laptop, just hold down the power button for about 10-15 seconds to turn the PC off. If that doesn't fix the problem, try one of the solutions below.

3. Battery Check
Sometimes you have to take that "have you tried turning it off and on again" advice to the extreme. Shut down the laptop, remove the battery, wait a minute or so, replace the battery, and boot up the laptop.

4. Driver Problems
This problem crops up if you install third-party software often and/or you turn your machine off all the time without using the Shut Down command.
Check the Device Manager on your laptop. If the keyboard line item has a yellow exclamation point next to it or if the keyboard icon doesn't show up at all, go to your laptop manufacturer's download page and install the latest drivers for the keyboard. You may have to hook up a USB keyboard (see below) to navigate text entry fields, but after you find the correct file it should be a quick download and fix.

5. Defective Keyboard
If you're still in your warranty period or have an extended warranty, then try your laptop manufacturer's tech support line. If they determine you're using a defective keyboard, you should be able to get it replaced at a service depot without too much hassle.

I hope this helps.

Regards,
Lokesh