Hi and welcome to the Gigabyte Forum.
Make sure that you are using the latest drivers for the USB3 chip and also the latest BIOS for the motherboard. If updating the BIOS please use QFlash for the procedure as it is safer.
Download the BIOS file from the website.
Take a USB pendrive and make sure it is formatted with a FAT32 file system. If the file ends with .exe run it, or if it is a zip file Unzip it, and save the files (usually contains 3 files) that you just expanded to the Boot sector or a folder of your choice on this drive and insert the pendrive into a USB port.
Re-boot.
Press the"End" key as the computer is POSTing and you will be taken into the BIOS flashing utility "Q-Flash". At the QFlash homescreen disable the Keep DMI Data option before proceeding. From there just follow the prompts to find your file and DO NOT TURN OFF THE POWER under any circumstances. It will look for the pendrive with the file on it and use that to update the BIOS. One thing to note is that the pendrive may show up as a floppy or hard disk instead of a USB drive. Once it has completed you can reboot. Believe me it is not as difficult as it sounds.
We have since found out that the problem with getting some motherboards to "see" the USB drive is a case of using as small a drive as possible, well at least under 2Gb, and even then some will be seen and some won't. Just a matter of luck.