Dryer isn't drying clothes. I've tried all of the common solutions (I think)
There should (must?) be a vent on the roof.  If you can get up there, take the hat off of the vent and run a fishtape though the vent.  (A fishtape is long, skinny, flexible steel or fiberglass rod that electricians use to run wire through conduit.)  Once you've got the fishtape to the other end, tie a nylon rope to the tape and pull it through.  After that, tie an appropriately-sized round vent brush to your rope.  I'd also tie a rope to the other end of the brush.  Now pull the brush though both ways a couple of times.