Take a look at this post I created. In case if Rachio 3 doesn’t work with your Master valve for whatever reason, you can buy this simple DIN rail Contactor to get the issue fixed. If it worked fine and suddenly not working, it may be possible that your valve is damaged or got shorted/ or faulty. It does happen.
However, as an alternative, I got multiple valves working using external power supply, with low budget system which is pretty solid. Let me know if you have any questions. I would be happy to help with Master valve Operations.