Assistance with Setting up NetRestore, NetInstall and NetBoot on Apple macOS Server

I require assistance getting NetInstall, NetRestore and NetBoot to work on my macOS server (10.13.6) and my network. It's a very simple network and the server is not setup in any special way but for some reason I can not get a NetInstall, NetRestore or NetBoot image to appear on any devices connected to the network. Here is what I've done and tried. I tried with both Mac OS X 10.11 Server and now macOS 10.13 My network is very simple. Router is a D-Link DSL-2890AL (located at: [login to view URL]). It is connected to a 5-port Gigabit switch. The server and all other devices are connected directly to that switch. The server is running macOS 10.13.6 and is located at: 192.168.1.1. I have tried creating a NetInstall image using the 10.13 install, it has corrected successfully and shows in macOS Server as an available NetInstall image. I have also used AutoDMG to create a basic disk image of 10.13 and using System Image Utility to create a NetRestore image, this also shows as available on the server. Neither is visible on target machines, not when option booting or from System Preferences. I have tried to see the NetInstall and NetBoot images on various target machines including: iMac 21.5" 2013, MacBook Air 2013, MacBook Air 2014, MacBook Pro 2015, Mac Pro 2012 etc. None show either network bootable volume. I have restarted the server, I have restarted macOS Server, I have tried different cables, I have tried connecting the server and the target directly to the router without the switch in between, I have pointed port 67, 68, and 69 to my server from my router, I have pointed 80 and 443 to my server. I have restarted my router. I'm out of ideas and I am seeking a macOS Server expert with experience in setting up networks and servers to deploy NetRestore, NetInstall and NetBoot images