First check if the valve is switched on. When switched on, the LED flashes briefly at regular intervals. How to turn your valve on or off you can find here.
If the valve is on, check if the LED is flashing red. If it flashes green, it can not be detected by the controller. For the valve to flash red again, it must be reset. More here.
If you can not turn on the valve, the battery may be exhausted. This can happen if, for example, the valve did not see sunlight during the winter break and remained switched on. Therefore, always switch off the valve during the seasonal break. Put your valve in full sunlight for a while, so it can recharge your batteries. After a full day of sun, it should turn on again.