@misterjroc First let me start out by shaming you. Masking a private IP address range doesn’t help us help you. There is no way if I was a hacker to know how to reach a 192.168.x.x subnet from the internet. If you were debugging using a public IP address (as in an internet address then I would suggest masking the address).

Since you mentioned the tftp address is your router/isp router I can make a few guesses.

SoHo routers are broken in that they almost aways give our their IP address as the dhcp next-server address even if they let you define a next-server value (the exceptions I’ve seen are ddwrt/openwrt and pfsense those work correctly). You have 2 dhcp servers on your subnet. One is your isp router and the second one is your 2019 server.

Two routers would explain this condition you explained. You are getting into the iPXE boot loader so your main dhcp server (Windows 2019) IS working because the iPXE boot loader is running, Inside of iPXE it once again issues a dhcp request to find the IP address of what it thinks is the FOG server. In this case your ISP router is returning the query faster than 2019 server. So your router is winning and iPXE tries to connect to your router instead of your fog server.

OK so prove me right or wrong, here is what I want you to do. On a third computer (witness computer) install wireshark. Its probably best of this witness computer is on the same wired network. Use the following capture filter inside wireshark port 67 or port 68. Start wireshark capture, then pxe boot the target computer. You will see a complete DORA cycle (DISCOVER, OFFER, REQUEST, ACK) This will be the pxe rom on the target computer getting the info to load iPXE, then when iPXE starts you will see the DORA sequence again. PXE boot to the error above. Now stop wireshark. If you have one or more OFFER packets those packets come from DHCP servers that heard the DISCOVER packet. If you only have one OFFER packet then we need to dig deeper. I’m thinking you will see two or more OFFER packets. The sending IP address will be listed in the OFFER packet.