Cause 1: Hardware Problem
One of the biggest causes to not be able to boot from USB is because the USB medium itself, the quality on how they are made and how internally works can affect a lot, for example there’s some memory sticks that are slower to startup, and so since the BIOS has a limited time to recognize them, if they don’t show up in the limited time the bios timeouts and skips it.
Solution
- Try with various USB sticks, they are cheap, and use common trademarks
- Don’t try to make the computer directly recognize and boot it, instead, pick the “Fx” option that shows up the menu to select from which device to boot from, on that way you give more time to the USB to be initialized and you make sure that the system will try to boot from it since it is meant to be listed.