For PXE boot from a CPU server, I don't remember all the configuration, but I remember that you have to create a file with the MAC of the Ethernet client that you are using for pxe boot.

You have to create a file with the name of the mac address, and then you have to copy the content of the default file. Then you can edit it to your needs, or you can mix the content of the default file with the content of example-pi file and try to find the configuration that works for you.