DIAGNOSIS: The most common cause is a full or clogged filter. The G30's cyclone system loses all suction if the filter is saturated or the air path is blocked.
FIX: Empty the dustbin. Now remove the filter and tap it firmly against a trash can to dislodge fine dust. For a deep clean, rinse it with water and let it dry for 24+ hours COMPLETELY before reinstalling.
IF THAT DIDN'T WORK: Check for a clog in the robot's intake (where the bin sits) and the bin's own air exit. Use a vacuum hose to reverse-blast any blockage. Also ensure the main brush is installed correctly and spinning.
HEADS UP: Never run the vacuum with a wet filter. It will ruin the motor. You need a spare filter to swap in during cleaning cycles. Replace the filter every 2-3 months with heavy use.