My USB device won’t show up at all in BIOS
Try using a different USB device, port, or USB hub.
My development platform won’t boot from a USB drive or microSD* card
First, make sure that your microSD card or USB device is securely connected to the development platform. Also make sure you don't have a microSD card and a USB drive plugged into the development platform at the same time.
Then try booting your board and changing the boot order to boot from your bootable device first. You may also want to try redoing the steps to create your bootable device and rebooting the development platform. For detailed steps, see Creating a bootable device and Installing your operating system.
For users of Reference Operating System for IoT: Be sure to extract the .xz archive file and write the Reference Operating System for IoT image to the bootable device, not the archive file! See also Acquire Target OS File to Install.