Here are some troubleshooting steps that may help in solving the issue.
- First is to uninstall/reinstall the keyboard driver.
- Go to Device Manager and uninstall the keyboard driver then reboot the laptop.
- After the reboot do test it again and see if it will work or not.
- If it will still not work open onscreen keyboard (just search for osk) and press the letter j and see if it will type the letter using it.
- After pressing J using OSK try pressing that letter again using the keyboard itself and see if it will work or not.
- And lastly, try connecting an external USB keyboard and see if everything will work normal using it.
- If it will work just fine that problem is that specific key only, try to dust off that key and see if it will work or not.
- Replacing the whole keyboard would be the only solution if all these will not work.