One of the easiest ways to determine if there is a problem with the controller is to take it totally out of the loop. Connect the wires for one valve directly to the transformer that powers the controller and see if the valve turns on without the controller. Of course there's always a chance there's something wrong with the power source (bad transformer, GFCI receptical that has popped, etc). So one other option to completely remove the power source and controller from the equation is to try three 9 volt battereis. Connect 3 batteries in series to get the 27 volts needed to open the valve. If you can't open it with batteries, then your batteries are bad, the selinoid in the valve is bad, or there's a problem in the wiring.