Secure Boot is Off. I promise and I hope I’m smarter than that. 
Time will tell I guess.
But, I will admit, I know next to nothing on iPXE, UEFI boot and FOG. This is my first go at it. I was able to image (capture/deploy) multiple times on this setup to systems that used Legacy ROMs and PXE. I’m probably making some seriously wrong assumptions about iPXE. And I apologize if I’m asking some very noob questions. Just not finding information quickly in the WIKI around troubleshooting this particular error.
So, I’m using a Ubiquiti Security Gateway for the DHCP server. I’ve used both Windows DHCP, and other Firewall stacks and all have worked. I suspect it’s the undionly.kpxe file that I’m using?
And it’s not network. I’ve got an unmanaged switch sitting between FOS and the host in question so all traffic stays local except for the DHCP ARP packet.