That's because the usb flash device is not picking up and it is booting into uefi Shell.
Try the hp format tool and win 98 boot files to fix the flash drive and see if it will boot to dos.
If it will, then re-run the forum flash tool on the flash drive...
Try the hp format tool and win 98 boot files to fix the flash drive and see if it will boot to dos.
If it will, then re-run the forum flash tool on the flash drive...