Controller not supplying power to valve. Main water supply turned off. Flow control stem turned all the way down. Check controller for valve power output. If no output is detected at controller, service controller.
Check valve solenoid for valve power input.
If output is detected at controller, but no input is detected at valve, power wire is broken or damaged. Isolate wire problem and repair. If power input is detected at solenoid, but valve still is not operating, turn water off. If other solenoid operates valve, replace solenoid. If other solenoid does not operate valve, continue troubleshooting.