How can I fix an “Invalid Signature” Secure Boot violation on my Omen PC?

Check that Windows is installed in UEFI mode before changing anything else. In Windows, open System Information and confirm that BIOS Mode says UEFI. You can also open Disk Management and check whether the Windows drive uses GPT. If it was installed in Legacy/MBR mode, Secure Boot may reject the bootloader; the drive would need to be converted to GPT or Windows reinstalled in UEFI mode. A USB installer should be booted from the BIOS entry labeled “UEFI: [USB name].”

Since the PC boots normally with Secure Boot disabled, the problem is probably with the UEFI boot configuration or the Secure Boot keys rather than Windows itself. In BIOS, make sure the system is set to UEFI-only mode and that Legacy Boot or CSM is disabled. Then look for an option such as “Restore Factory Keys,” “Install Default Secure Boot Keys,” or “Reset Secure Boot Keys.” Save the changes and reboot. Don’t manually delete partitions or change disk settings unless your important files are backed up.

If restoring the default Secure Boot keys doesn’t help, download the latest BIOS update specifically for your exact Omen model from HP and install it using HP’s official instructions. Also verify the date and time in BIOS, since an incorrect clock can sometimes interfere with signature validation. Avoid using unofficial BIOS files or forcing Secure Boot on repeatedly if the system keeps reporting an invalid signature.