Conman is acting as a DNS proxy conflicting with the pihole-FTL binary.
Checkout the "--nodnsproxy" directive on the man page:
I believe Jessie still uses System-V to manage services/daemons.
Look for a connmand Bash script in below folder:
/etc/init.d/
Edit the script file manually and add that "--nodnsproxy" argument to the line with the connmand executable (which connmand).
Restart conmand:
sudo service <CONNMAND_SCRIPT_NAME> restart
Or
sudo /etc/init.d/<CONNMAND_SCRIPT_NAME> restart
Restart Pi-hole:
sudo service pihole-FTL restart
Or:
sudo /etc/init.d/pihole-FTL restart
And check ports used by Pi-hole:
sudo netstat -nltup | grep 'Proto\|:53 \|:67 \|:80 \|:471[1-8] '