At the garage
A tripped GFCI, an unplugged transformer, a dead display, and a sensor parked on bypass or on active all look like “it will not turn on.” Reset the clock’s time after any of those, because a blank clock often comes back with the wrong day.
At the valves
If the display is alive and manual start still does nothing at every valve, the common wire or the supply valve is next. Call 346-642-6161 and say whether the display is lit.