Dryer exhaust not blowing out of vent tubing

Question

My machine washes and then goes into the dryer mode fine. But the vent/exhaust doesn't seem to be working. At one point, the hot exhaust air even came out of the front where you put the detergent/softner, but not the exhaust hose. I've cleaned out the exhaust hose as much as i can without improvement, but it's only a small hose outside of the dryer. Any suggestions?