@FiskTechLV What exactly is the PXE rom reporting as an error code? It should be a EXX-XXXX like error code.
The next step is going to be a little involved, but it will give us a better idea of what is going on in your network. As long as the fog server and target computer are on the same subnet you can run this command from the fog server. Make sure tcpdump is installed on your fog server then run this command.
tcpdump -w /tmp/bootup.pcap port 67 or port 68 or port 69
Then pxe boot that target computer until you get the pxe boot failure. Once you reach the error then stop tcpdump and post the pcap file here. I might also suggest if you have some networking skills, load the pcap file into wireshark and see if you can spot the error. But also post the pcap here.