I would check connection on the other end of that wire, do you know where you zone 1 valve is? Most likely the wire is connected to the valve using a twist on cap connector, if original connection has been done poorly the wire could have came loose and disconnected. It is also possible that the problem is with the other (common) wire connected to zone 1 valve through a similar, likely twist type, connector.
If both of the connections are fine, you can try checking the valve using a 9V battery. Connect it to the valve wires (when they are disconnected from Rachio) and you should hear some actuation, otherwise the valve may need to be replaced.