Agreed, did you physically check the splices at the valves, or just do a visual? I have seen connections still in the wire nut before, but not making good enough contact to work. You may want to re-do the splices if you already have the ground dug up, just to see if it helps. Sometimes just a visual isn't good enough. Also, the ends of the wires may have become corroded and are no longer good conductors. You may have to strip back some wire and make a new connection. If there aren't any splices anywhere else in the yard, and all other zones are working normally, it has to be the wire at the valve or the controller. If this valve shares a common with the other valves, and the other valves work, suspect the zone wire, unless it is the last valve to be connected to the common, then check both again.
Tony Posey
Ridge Run Landscapes