Insert the USB drive in the lower USB port. The upper one would not boot for me.I just bought this is a DIY and added a SODIMM and mSATA 32 GB drive to it. I downloaded the pfSense memstick image and used Rufus to create a bootable USB stick. I had my keyboard already plugged into the lower port at that point, so I just inserted the USB stick into the upper port. Tried booting from it, tinkered with BIOS options, nothing worked. It's like it could not "see" the drive.So then I tried swapping ports on a whim and boom, the unit saw the drive, and everything was fine after that.