Check the voltage output at the controller for the zone in question.
Do you know the physical location of the valve you activated the previous day? If so, find it and activate it manually from the valve’s manual bleed screw. If it activates, It’s probably a loose wire or splice. If it doesn’t activate, it’s probably a hydraulic issue. In this case, it could be a diaphragm.
If it’s a hydraulic issue, Rachio does not know this by the controller. If it’s electrical, Rachio can detect a fault, but not an open wire.
Most likely a coincidence, though. I’ve been on site doing system checks many times and have had valves fail while I’m testing the system. They’ve failed electrically and due to diaphragm issues.
Welcome to the neighborhood!