There should only be power to one solenoid when one solenoid is turned on. There might not be enough voltage from the controller to pull in all the solenoids at the same time. Try disconnecting all but one and see what happens.
Thanks. To make it more interesting: I noticed that the jump wire is still present on the controller terminals for the rain sensor. Which confuses me since I had an RSD rain sensor installed at the same time the whole system was installed. So I walked over the rain sensor, and I see that the wire going into the ground is shredded, I guess by the lawn mowing service. I spliced the wires (red to red, black to black). I go back to the controller and voila all the sprinkler zones work again. If I take voltage readings, the zone that is on is ~26, and all others are just background low low low voltage.
At the controller, I see one black wire that dead ends to NOTHING, not connected to anything. And one wire that connects to"Zone 8." To be honest, I am not sure whether I have 7 or 8 true sprinkler zones.
But is connecting one (red) wire of the rain sensor to a random valve terminal a valid way of connecting a rain sensor? Is there any chance that that would work? Are there reasons that an installer would not connect the sensor wires to the Sensor terminals of the controller?
Thanks, I really appreciate our help. So I have the zones working again, but still puzzled on how this weird connection of the rain sensor fits in.