Vacuum will not start; display or app shows “Err 1” shortly after pressing the Clean/Power button.

Safety first: Turn the vacuum OFF and disconnect the charging dock from the wall before handling the battery. Do not short battery terminals.

• Remove and reseat the battery: Open the battery compartment (usually on the underside or rear handle). Slide the battery pack out, inspect the contacts for dust or oxidation, then firmly reinstall until it clicks into place.
• Clean battery contacts: Use a dry microfiber cloth or a pencil eraser to gently clean the gold battery terminals on both the pack and the vacuum. Do not use liquids or metal tools.
• Try a full reset: With the battery installed, press and hold the main Power/Clean button for 10–20 seconds (or Power + Home if applicable) until the unit beeps or the lights cycle, then release and try to start again.
• Test charging: Place the vacuum on the charging dock or plug in the charger. Confirm the charge indicator lights behave normally (pulsing or solid per manual). If the error returns immediately off the dock, the pack may be defective.
• Replace battery if needed: If reseating and cleaning contacts do not clear Err 1, replace the battery with a genuine iRobot lithium‑ion battery pack compatible with your cordless model.

Stop using the vacuum if the battery is swollen, leaking, or excessively hot; dispose of it according to local e‑waste regulations.