DIAGNOSIS The cleaner head's clutch mechanism has likely disengaged due to a high-resistance event, or a severe blockage is present in the drive path.
FIX 1. Turn off the vacuum. 2. Press the red cleaner head release button and detach the head. 3. Manually rotate the brush bar by hand. Clear any wound fibers, hair, or debris from both ends of the bar and the entire length. 4. Reattach the head firmly until it clicks. The brush bar should spin when the vacuum is turned on and the head is flat on the floor.
IF THAT DIDN'T WORK The clutch may need to be manually reset. With the cleaner head detached, locate the clutch knob (grey/silver, connected to the drive belt). Turn the knob clockwise until you feel it click back into its engaged position. Reattach the head.
HEADS UP The brush bar is designed to stop if resistance is too high to prevent motor damage. Regularly clearing hair from the bar ends is required maintenance for high-pile carpets.