sudo systemctl status reef-pi.service
sudo journalctl -fu reef-pi.service
Connecting reef-pi using a TTL cable. Adafruit has an excellent tutorial on how to use USB TTL cable to configure raspberry pi, in cases where display and keyboard is not available.
Check reef-pi version (helps in bug reports)
sudo systemctl stop reef-pi.service sudo rm -rf /var/lib/reef-pi/reef-pi.db sudo systemctl start reef-pi.service
One of the common reason gotcha is dev_mode being enabled. Dev mode allows reef-pi development in non-raspberry pi system and it mask all physical control (they are faked out). Make sure dev_mode is disabled or unchecked, under Configuration -> Settings -> Capabilities. Note: changing any of the capabilities will require a reload to take effect.
Check if time is configured correctly: All of reef-pi timers and almost all periodic tasks rely on system time. Make sure timezone is configured correctly using raspi-config.
What information to share when asking for help? If you are still stuck, feel free to reach out to reef2reef thread on reef-pi. Please note down reef-pi version, Pi version, circuit details (an image will be very helpful) and shared those details while asking question. They help deducing the issues faster.
Troubleshooting circuits: Check voltage at every connection. Ends of jumper pins. Check for continuity before wiring.