Cleaning the Visual Docking Target and Charging Contacts
Inspect the visual docking target and charging contacts to make sure that they are clear of debris. Wipe with a clean, dry cloth.
Note: Do not spray cleaning solution directly onto sensors or into sensor openings.
https://manuals.plus/irobot/j7-roomba-robot-vacuum-cleaner-manual#ixzz7qWTeLHrE