Only one of the two lanterns is working, what do I do?

Check the lantern that is not lighting on its own:

1. Confirm the bulb is seated securely and try the bulb from the working lantern in it.
2. Confirm the sensor cap has been removed if you are using the automatic Dusk-to-Dawn mode.
3. Check that the wire connections at that fixture are secure, and that no other light source is shining on its sensor.