My computer was forced to install an update, and afterward it stopped at this message: "SECURE BOOT VIOLATION — Invalid signature detected, check Secure Boot Policy in Setup." I tried restarting so I could press F2 and enter the firmware setup, but once I reach that point, neither my keyboard nor mouse responds. I've also tried the black USB 2.0 ports. Could the update have changed the Secure Boot keys or firmware settings, and what steps can I take to recover the system?
2 Answers
Try a very basic wired USB keyboard in a different port, preferably a rear USB 2.0 port directly on the motherboard. Avoid wireless devices, USB hubs, front-panel ports, and adapters. If that still does not work, disconnect every unnecessary USB device and try again. Some systems also have a clear-CMOS or BIOS-reset procedure that can restore input and firmware defaults, but follow the exact instructions for your motherboard or computer model before doing that.
This usually points to a Secure Boot key or firmware configuration problem rather than a normal Windows setting. If you can reach the firmware setup, look for an option such as “Load Default Secure Boot Keys,” “Install Factory Keys,” or “Restore Secure Boot Defaults.” You may also need to check whether the boot mode is set to UEFI. If the update included a BIOS or firmware component, your computer manufacturer may have a matching firmware update or recovery procedure.
The problem is that I can’t get into the firmware setup because the keyboard and mouse stop responding before I can use F2.

I already tried the black USB 2.0 ports, but I’ll disconnect the other devices and test with a different basic keyboard.