I have an asus x540La laptop. I have a usb with ubuntu 16.04 on it. Somehow, my bios does not see the usb drive. I saw it at one point, so I know it should work, but somehow the usb drive is no longer accessible in the bios settings. I have no idea why it disappeared. I didn't do anything all that crazy, but it worked once and now I cannot choose the usb boot option.

I don't have any knowledge or experience with bios. My thinking is that if I flashed the bios with the same version it has now, the default settings would come back and I would be able to select the usb drive for booting.

My problem is that the Flash function in the bios settings doesn't see the usb drive either, so I can't do the flash.

I figured out my problem. My usb drive was faulty. Thanks anyway!