Dell PowerEdge R720 Boot Problem

Hello,

I have a Dell PowerEdge R720 server I am trying to install free Nas on. I have disabled the Raid controller.
I have installed to a USB stick to the front USB ports using the live CD on Version 9.2.1.5

I have seen other users on the Dell R710 having to set USB emulation to HD but I cannot find this setting anywhere in the Bios. I have updated the BIOS to Version 2.2.2

when I try to boot from USB i get the following
F1...

Dell PowerEdge R720 Boot Problem