Sprinklers stopped working

I just installed the gen 2 yesterday. All the zones tested fine. I ran two stations in the evening. Ten minutes later I did a quick run on three other stations but no water was coming out. The controller showed the sprinklers were running but no water was coming out. I believe I checked everything I could. It was already dark so I had to stop. Today when I got home around 2:00pm I tested zone one and it worked. Do you know what caused this?