@esmatos Well the error is saying that the boot file needed is not found.
I can say that pfsense does work with fog. You need to make sure you fill out the Network Booting section properly.
Enabled: Checked
Next Server: (ip address of fog server)
Default BIOS: undionly.kpxe
UEFI 32 bit: i386/ipxe.efi
UEFI 64 bit: ipxe.efi
If that doesn’t work then lets grab a pcap of the pxe booting process as long as the FOG server and pxe booting client are on the same subnet you can use the FOG server to capture the pcap: https://forums.fogproject.org/topic/9673/when-dhcp-pxe-booting-process-goes-bad-and-you-have-no-clue