Please try these options one by one and check after each option.
- Run Keyboard Troubleshooter
Type Troubleshoot in Windows Start Search box > Click Troubleshoot > Scroll down and click Keyboard > Run the troubleshooter > Follow onscreen directions
- Uninstall Keyboard Driver
Windows Key+X (Or right click on Start) > Click Device Manager > Expand Keyboards > Right click on Standard PS/2 Keyboard > Uninstall > Reboot the computer to reinstall
- Turn off filter keys in Ease of Access
Type ease in Windows Start Search box > Click Ease of Access > Click Make the Keyboard easier to use > Ensure Turn on filter Keys is not checked