Fuse has blown. Replace the fuse with one of the same amperage rating. If the fuse blows again on a particular station, that station's solenoid or field wires may have a short circuit that needs repair.
Power is off to the controller.
Determine why power to the controller has been interrupted, and re-establish power. Display is blank. If the controller is still receiving power, an electrical surge exceeding the controller's built-in surge protection may have damaged the controller's microprocessor. Shut off power to the controller, open the lower face panel, and disconnect the battery. Reinstall the battery and turn power back on.