Larger debris is usually the responsibility of the brushes. Remove the bin and run the Roomba-- are the brushes actually turning? If not, call customer support for a new cleaning head module. If so, remove the grill from the back of the bin. Make sure that the little fan inside is clean, then reinstall the bin on the Roomba and run it. If that little fan doesn't spin, your Roomba has lost vacuum suction and you need a new bin.

Fan is spinning but nothing makes it into the fine dust bin like when it was new. The big stuff gets into the large item bin because of the brushes. All the fine dust accumulates around the rubber strip. Does someone make a stronger Fan for these units?