I have downloaded and written latest ISO image of Debian as instructed on this https://www.debian.org/CD/faq/#write-usb FAQ page... I've tried both cp and dd methods, I've also tried the Ubuntu (current OS in use) Disks, Restore Disk Image process... in all cases the ISO is copied to the USB, but when booting and selecting F10 to show bootable devices, the USB is not shown on the list. I know my EFI BIOS is configured correctly as I am able to see a Ubuntu ISO on the boot list on a different USB drive. I have also tried writing the debian image to the USB drive that I know works for Ubuntu just to rule out any issues or differences between the USB drives, and it still doesn't show on boot menu. Any assistance or ideas would be greatly appreciated. Thank you.
The problem that I have had with a lot of motherboards is the lack of firmware support for USB3.0 ports at POST; which means that you generally cannot boot from USB ports other than the USB2.0 ports. This may be the case in the OP's scenario.