If you’ve changed your IP address, there are a number of files you need to change.
/var/www/fog/lib/fog/Config.class.php use "grep -r <old fog server ip> /var/www/fog/lib/fog/ " and find any references you missed there /tftpboot/default.ipxe /etc/hosts /etc/dnsmasq.d/ltsp.conf /etc/network/interfacesFull list is here
https://wiki.fogproject.org/wiki/index.php/Change_FOG_Server_IP_Address