Support replied quickly with the following fix
”
Many BIOS will rearrange the boot order when you add new devices. You should reconfirm that the flash drive is the first device in the order. Additionally, many BIOS prefer that you set the hard drive to be the first boot device, but within the hard drive priorities you have the option to set the flash drive as the first "hard drive" to boot from. “
will edit as Solved
Thanks!