is the boot image, on the USB, UEFI bootable?
usually if the USB is capable of booting in UEFI mode, the USB will show up twice in the BOOT Menu.
Try enabling Legacy mode in the BIOS and see if you can boot of the USB. If it boots, the USB is not UEFI bootable.
I used a program called rufus which a friend told me would create a UEFI boot-able USB drive