The sealer works great, most of the time. Sometimes that bag does not seal so I have to turn it around and try again.  Sometimes several tries to get it to work.  When creating the custom bag size I find that the bag does not seal.  I fill the bag and then seal the top.  The bag is a little larger than needed to allow me to cut the bottom seal off and then reseal it like the top was done. This has worked on all occasions. The sealer is several years old and that may be the problem.