DIAGNOSIS The battery is in a deep discharge protection state. This happens if the robot sat off the charger for months or the base lost power.
FIX Manually place the robot on the charging base. Ensure the base is plugged in and the power light is on. Leave it there for at least 24 hours without interruption. Do not press any buttons. The blue light should turn solid after several hours.
IF THAT DIDN'T WORK The battery may be dead. After the 24-hour charge, try a hard reset. Hold the power button on the robot for 10 seconds. If still unresponsive, the battery needs replacement.
HEADS UP If storing the robot, leave it on the charging base. The base maintains a trickle charge to prevent this.