It could be a variety of things, forecasted precipitation, crop type, existing irrigation events.
I would check out the webapp app.rach.io - - > Zone - - > soil moisture level which shows the graph of each Zone and why or why not something will run.
firstname.lastname@example.org can help explain why there is no upcoming watering events as well.
Hope that helps. Without details regarding weather or crop type it's hard to give an accurate answer.