Apologies first of all if this is a question that the is a no brainer but I am a landscaping newcomer and havent the slightest clue what to do. I have a brass 3/4 Orbit Anti-Siphon valve. It does not turn on when the timer says it should. I replaced the solenoid (2xs) and it is only when I unscrew the bleed screw that the sprinklers go off. When I tighten it up, the water stops. Am I doing something completely wrong here?

Thank you in advance for your help!