We are replacing an old NetBoot server and after setting up the new NetBoot server (OS 10.12.6, Mac Mini Late 2014) and testing it out with a 10.12.6 NetRestore image, we're having trouble booting from the NetRestore image at some of our sites. The images will show up, but when you try to boot from it, it just boots from the internal HDD. I verified that the server is fully functional at one of our sites by bringing the server and the same computer down there and testing it out there. This is actually the same issue we had with our old NetBoot server. In the past, from what I understand, rebooting the server has helped resolve this issue temporarily, but I have been unable to get the new server to work at all at this site.
I've looked into "blessing" the server, trying new NetRestore images, changing "Availability" from HTTP to NFS, trying multiple computers. The NetRestore images are created using System Image Utility. We have not set up anything else like DeployStudio, yet.
Another separate, but possibly related issue is, the NetBoot images don't show up at all sites. They only show up when it's on the same subnet as the server. We are currently connecting the server to the same subnet and VLAN as our DHCP server. We are also use Cisco switches.
Thanks in advance for any help!