The swap test
At the controller we move the dead station’s wire onto a terminal that works. If the valve then opens, the clock is fine and the wire or the solenoid is not. A toner or a careful excavation finds the break. We splice with connectors made for wet soil, not a twist of electrical tape.
The common is shared
If every station died at once, suspect the common wire, the transformer, or the controller, in that order. Call 346-642-6161 and say whether one station or all of them went quiet after the digging.