Installing windows 10 over Ubuntu16.04 LTS; W10 Installation USB not being read

You can create a Windows bootable USB from Ubuntu through winusb

Install it:

sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt update
sudo apt install winusb

Create it :

sudo winusb --format </path/to/windows.iso> <device>

Use sudo fdisk -l to get the right <device>

Also you can use unetbootin montionned on @AFH comment's :

sudo apt-get install unetbootin

From the BIOS settings set the USB on the first boot order (verify the legacy boot order and the UEFI boot order too) . Or you can select to boot from USB directly (It depends on your BIOS manufacture)

in addition to @Blaine answer: sometimes the USB flash itself is the problem. i have a 8 GB transcend that cannot boot anything for some reason, no matter what option you choose in BIOS or what have you done to it to make it bootable. try changing the USB Flash. Might do the trick