Dryer venting, especially gas fired ones, should be solid piping. Joints should be taped, not screwed.
Electric dryer, five foot sections, solid dryer vent pipe, taped joints, no flex pipe.
I've seen plugged dryer vent pipe before, but that's really plugged dryer vent pipe.
Doing inspections of triple deckers, it's amazing what people, even so called professionals, try to do.