What are you using for a weather reference? (Settings, Weather Source) Best is a Tempest, but 2nd best is a solid 24/7 local weather station near you. If you’ve specified a weather station, connect directly to it via Weather Underground and look at its recent history. If it indicates lots of rain, and you’ve had none, something is amiss. Select another station or the Weather Network setting.
Your zones have “capacity” for water, which Rachio will manage so the root depth of your plants is sufficient. You can look at each of your 4 zones to see its Soil Moisture percentage which when tapped shows you a graph of the depletion and filling of the zone’s profile. You’ll see water coming in (from irrigation or nature) and out (Evaporation, transpiration). Goal, of course, is to keep everything growing and working for water so your irrigation is minimized and your plants are tough enough to handle the swings. You don’t have to assume how it works… there’s lots of online help on this site for all the setup you might need to do. Rare that either that or this forum or you can’t figure it out.