keyboard is not working

@sapnarawat93898 sounds like it's time to replace it. you did not give us a lot of details so I assume you checked everything else and did a reboot and check in safe mode with whatever OS your computer is running. If you ruled out software and settings issue, replace it. Download the service and maintenance manual for your HP 255 G8 (7N4W2AA) from here Page 56 will show you what needs to be done.

Just like most other new systems, your keyboard is part of the top cover assembly.

keyboard not working