Run the robot in the water without the filter bag.
If the robot runs normally, without the filter bag, the filter bag may be clogged.
Wash the filter bag in your washing machine on gentle cycle, cold water, NO detergent.
Or, hand-wash the filter bag in a 5 gallon bucket of water. This will release the dust particles from the bag into the bucket.
Reinstall the bag and run the cleaner.