ISC-DHCP-SERVER failed, but issues IP fine

I am running a PXE service on buster.

On a client it searches for a DHCP server, for about a minute. Then eventually times-out. Meanwhile on the server sudo systemctl status isc-dhcp-server.service reports …Active: failed (Result: exit-code)… . Then I issue sudo systemctl restart isc-dhcp-server.service - reply: Job for isc-dhcp-server.service failed because the control process exited with error code.… .

However back on the client, I restart it and again it searches for a DHCP server. In a second or two it is assigned an IP … (This happens on each boot - as it should.)

So in order to discover more, on the server, sudo systemctl status isc-dhcp-server.service gives me the PID. Then journalctl _PID=<PID> gives all the messages: … DHCPINFORM from x.y.z.xx via wlan0 and … DHCPACK to x.y.z.xx (a:b:c:d:e:f) via wlan0 - over and over.

• Are there really errors?
• Why does the daemon report failed (with non-error responses) when it works?

I think you want to figure out what is going on with your DHCP server first and why it isn't reporting good status. Run this command to get the journal entries as to why it is failing as a good start: journalctl -u isc-dhcp-server