Make sure open end of bag is resting entirely inside Vacuum Channel. If edge of bag is beyond Vacuum Channel, bag will not seal properly. Examine bag for leaks. To see if your bag has a leak, seal bag with air, submerge it into water and apply pressure. Bubbles indicate a leak. Use a new bag if bubbles appear. If you are using a custom-sized FoodSaver® Bag, check seal of bag. A wrinkle in the bag along the seal may cause leakage and allow air to enter. Just cut bag and reseal. Do not attempt to make your own side seams for a FoodSaver® Bag. The bags are manufactured with special side seams, which are sealed all the way to the outer edge. Making your own side seams may cause leakage and allow air to enter.