I fired up my sprinkler system for the first time this year and all the zones were working fine except one of them. Nothing came on for a certain zone and I checked the control panel and the alarm light was on with Err and the zone number. I then went and manually turned on the zone from the valve box and it turned on, but seemed to have low pressure. Any ideas what this could be? I have a solenoid I could try, but not sure if that is the problem or not. Thanks!