resolved = systemd-resolved = resolved.conf

re-configure it if it has been installed but not activated

sudo apt update
sudo apt install systemd-resolved
sudo systemctl start systemd-resolved
sudo systemctl enable systemd-resolved

troubleshooting

Ref1

sudo systemctl restart systemd-resolved

journalctl -u systemd-resolved -f
systemd-resolve --status

In order to get more information from resolved you need to do service edit of via:

sudo systemctl edit systemd-resolved

[Service]
Environment=SYSTEMD_LOG_LEVEL=debug

sudo systemctl restart systemd-resolved

# to revert this logging change
sudo systemctl revert systemd-resolved
sudo systemctl restart systemd-resolved