Diagnosis
The red exclamation point is a general fault indicator. Most often, this is a blockage in the main airway or a filter issue preventing normal airflow.
How to Fix It
Perform a full airway check. One: Detach the wand from the main body. Two: Remove the cleaner head. Three: Visually inspect the wand, the main body inlet, and the cleaner head inlet for obstructions. Four: Remove and check the filter. Tap it clean over a trash bin. Reassemble. The fault should clear.
If That Didn't Work
The battery may not be seated correctly. Power off the vacuum. Press the red battery release button and remove the battery. Reinsert it firmly until it clicks. Power on.
Heads Up
The filter must be completely dry before reinsertion. A damp filter will trigger the fault. Allow 24 hours for air drying after washing.