Error 604 – Light level unchanged
This indicates that the sign’s light sensor (if equipped) hasn’t changed its reading in over one hour.
This may mean that the sensor has been disconnected from the sensor hub or otherwise can no longer be read.
This warning can be ignored in conditions where the light level is steady for extended time (such as at night), or if your sign is not equipped with a light sensor.
Contact your sign’s manufacturer for further information.