1. If you use the Windows Media Creation Tool, you don't download to the USB-stick. You download to the hard disk (as you always do) and then in a separate step you make a bootable USB-stick or DVD with the right contents.
2. Maybe the BIOS doesn't accept your choice if it doesn't see a bootable stick. Start with making that.
After two weeks of troubles with windows 10, 5 different Microsoft agents all with different advice, it was decided that I needed to do a clean install with a bootable USB. After Microsoft downloaded to my flash drive. I was told to change the Bios so it would boot to the flash drive first. Not that easy. My computer is a Gateway DX4860 circa 2011. No matter what I choose it won't "catch" it always reverts to the original selection. Gateway's website was useless as they only talk about newer Bios. Then I checked the flash drive and it was empty!! after three hours of downloading (I have a slow internet). I'm downloading again by myself but I will still need to change the Bios if the download works.. ANY suggestions appreciated.