You are going to have to explain a bit more how FOG fits into this picture. What LAN is the fog server on?
What LAN is the FOG server’s imaging nic connected to?
Where is your main dhcp server?
Do you have full routing between the subnets?
Do you have a dhcp helper service configured on your subnet router?

I found a solution. I am using WinNTsetup4 which I run from winPE and it works. I don’t know what else he does but it works so I won’t look. Thank you for helping me !

i solved my problem using undionly.kpxe file from a debian 10.4