DIAGNOSIS The robot's internal bin sensor is either obstructed by a dust clump or has failed. It's a common sensor issue.
FIX First, remove and empty the robot's onboard bin. Then, use a flashlight and a dry cotton swab to clean the small sensor window inside the robot's bin cavity. Reinsert the bin firmly until it clicks. Run a cleaning job.
IF THAT DIDN'T WORK The error might be with the Clean Base, not the robot. Empty the Clean Base's disposable bag, even if it's not full, and ensure the bag is seated correctly and the flap isn't stuck.
HEADS UP Never use a wet cloth or cleaner on the sensor window inside the robot; moisture can damage the electronics.