What am I doing wrong?

I installed isc-dhcp-server on Linux Mint 20.3

sudo apt install -y isc-dhcp-server
i followed this simple guide:
https://linuxhint.com/configure-dhcp-server-linux-mint/
i checked status:
isc-dhcp-server.service - ISC DHCP IPv4 server
Loaded: loaded (/lib/systemd/system/isc-dhcp-server.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since Sat 2022-03-12 10:32:42 CET; 14s ago
Docs: man:dhcpd(8)
Process: 7012 ExecStart=/bin/sh -ec CONFIG_FILE=/etc/dhcp/dhcpd.conf; if [ -f /etc/ltsp/dhcpd.conf ]; then CONFIG_FILE=/etc/ltsp/dhcpd.conf; fi; [ -e>
Main PID: 7012 (code=exited, status=1/FAILURE)

what I wrong?

thanks