When a winterized alert occurs, it means that the controller has been placed into a winterized status. All scheduled irrigation will stop indefinitely. This is expected behavior, and you do not need to do anything to clear the alert.

The controller will continue to receive daily ET values, but stations depletion remains constant. Manual irrigation, Runtime Valve Test, and MV Override are disabled.

How to Clear a Winterized Alert

When taking your controller out of winterized mode, the alert will clear on its own. 

To take a controller out of winterized mode in WeatherTRAK Central, mobile app, and from the controller,  read:
Controller Mode: Off, Shutdown, Winterize