Secure boot request for pin

[SIJU5]

I need to enter a 4-digit security code, but the computer isn't detecting the keyboard. The computer is an HP EliteBook 800 G4 Mini. Is there a specific way to enter this code, and which USB port should I plug the keyboard into?

[DGroves]

the front or rear usb ports should work if the keyboard is still not working try another keyboard

[Meghana_10]

Hello @SIJU5, Welcome to the HP Support Community.

If the HP EliteDesk 800 G4 Mini is asking for a 4-digit security code before Windows starts and the keyboard is not responding, the issue is usually related to pre-boot USB keyboard detection, rather than Windows keyboard drivers.
 

1. Connect the keyboard to a rear USB port

1. Shut the computer down completely.
2. Disconnect the keyboard from its current USB port.
3. Connect a wired USB keyboard directly to a USB Type-A port on the rear of the EliteDesk 800 G4 Mini.
4. Do not use a USB hub, docking station, or wireless keyboard for this test.
5. Turn the computer on and wait for the security-code prompt.
6. If one rear USB port does not detect the keyboard, try the other rear USB Type-A port. The G4 Mini has both USB 3.1 Gen 1 and Gen 2 Type-A ports on the rear, so trying another direct rear connection is a useful way to rule out a port-specific detection problem. 

2. Enter the 4-digit code

1. If the security screen is specifically asking you to enter a 4-digit code, simply type the four digits on the physical keyboard and then press Enter.
2. You normally do not need Windows or a keyboard driver for a BIOS/pre-boot security prompt. The keyboard needs to be detected by the system firmware itself.
3. If the keyboard has a separate numeric keypad and it is not responding, use the number keys along the top of the keyboard instead. This removes Num Lock or numeric-keypad behavior from the troubleshooting.

3. If the keyboard still does not respond

1. Try another basic wired USB keyboard, preferably one without additional software, wireless functionality, or a USB hub built into it.
2. Also try each rear USB Type-A port individually. If the keyboard works once Windows has loaded but does not work at the security prompt, that further points toward a pre-boot USB/firmware configuration issue, rather than a faulty keyboard.

If the prompt is actually inside Windows

• If you are already at the Windows sign-in screen and the 4-digit code is a Windows PIN rather than a BIOS/security prompt, the troubleshooting is different. In that case, you can use the Accessibility/Ease of Access option on the sign-in screen to open the On-Screen Keyboard and enter the PIN with the mouse.

For an HP EliteDesk 800 G4 Mini security prompt that appears before Windows starts, the recommended first test is a wired USB keyboard connected directly to a rear USB Type-A port.

If the keyboard remains completely unresponsive across the rear USB ports, let me know exactly what the security screen says and whether the keyboard works normally once Windows loads. That will help determine whether this is a BIOS/security prompt or a Windows keyboard issue.

Please check the link for more information - Maintenance and Service Guide HP EliteDesk 800 G4 Desktop Mini

Have a great day!