There are several reasons why a valve might not open. Please review the following checklist:
It is always a good idea to make sure the water supply to your irrigation system is on. Test the system manually at the valve location.
If the valve does not receive an appropriate level of voltage or the wire distance is too long, you may experience issues opening the valve.
There is an entry port from the valve upper chamber to the solenoid and an exhaust port from the solenoid to downstream in the valve. If either port gets clogged with debris, the valve may not open or open fully.