It doesn't look like the rain sensor is attached. I can't find a rain sensor at all along the house. I tracked the one wire I referred to earlier that stems off the main wire and it's not connected to anything. It looks like the end was ripped off and it just got buried.
Checking the system wiring for resistance, from the controller, will show infinite resistance on each zone, if there's a broken rain detector wire out in the field. The simple remedy in the case of the rain-detector wire being broken is to connect the two conductors to each other.
But we'd feel better if you went about this more methodically using a multimeter.