Failed getting ISO Disk (USB or CD Boot)

Question

Hello, 
 I am attempting to install Sophos XG Firewall on a Zotac ZBox MI542. I am able to boot multiple other operating systems (Windows Installers, Linux Installers, FreeDOS Boot Disks, XEN Hypervisor Installer, etc) from both USB and external CD-ROM. 
 Each time I attempt to boot the CD or USB key that contains the Sophos XG firewall, I receive an error stating "Failed getting ISO disk". This occurs on both boot media. I have re-downloaded the ISO multiple times and used both the dd and ISO writing methods on both OSX and Windows. I have converted the disk image to dmg using hdiutil, per the quick start guide, prior to using dd. 
 Is there something simple I am missing in order to get this ISO/installer to boot? 
 Josh

JoshuaSmith · Accepted Answer

Thanks Dwayne, Rufus did the trick. 
 ***NOTE: to prevent banging your head against the wall, when you click Start on Rufus it will ask you if you want "ISO (recommended)" or "DD" 
 Pick "DD"

N8XJA1 · Answer

JoshuaSmith - Simply choosing DD in Rufus (v2.15) resulted in a working boot USB drive. Thank you

DwayneSneade · Answer

I had the same issue with a downloaded ISO (SW-SFOS_15.01.0_MR-1.1-407) put on a USB stick made bootable with UNetbootin. I created another bootable USB stick with UUI and had the same issue. Finally I tried one more time with Rufus 2.7 and I am now in business.

john_kenny · Answer

Nice one Pal this worked for me, was first time Rufus sticks had ever given me issues!! Id always selected ISO write never DD write, but it worked in this case.. 
 Thanks again, 
 JK

Jelle · Answer

Used Etcher as currently described in this KB https://community.sophos.com/kb/en-us/126906 
 I think this KB formerly described the same with Rufus. 
 With Etcher it worked perfect on a Zotac Zbox MI620 nano which only has USB3.0 and USB3.1

Lars Holte · Answer

Same error here trying to install from USB (16GB Verbatim) with the SW-18.0.1_MR-1-Build396-396.iso loaded. 
 Tried Rufus (both with and without DD), Ethcher and RMPrepUSB_Portable_v2.1.745 all without luck, all software said ISO was written successfully without errors. 
 Turns out the USB stick was protected in firmware which made some of the stick read-only (but no errors when writing the ISO). 
 Switched to a different USB stick (16GB FlashVoyager GT) and (using Etcher to write the ISO) the problem was solved, XG installed successfully. 
 Regards, Lars