Edward, I had the same trouble with the sensor flaps. I’d enter a bag to seal it, hold it straight across… cut off a little of the bag… all the tricks to make it work but it just wouldn’t activate the vacuum sealer. Here’s what I did to fix it.

If you turn the sealer over and open the drawer you’ll see there are two floppy plastic pieces. You’ll also see the seal gasket that the drawer gasket seals press and seal against. If the flappers and seal rings are dirty and gummed up the sealer won’t work.

To clean them used a tooth brush (soft bristle) and brushed the goo off the flaps, top bottom and around the seal rings. I used awesome cleaner to spray the parts/pieces in there to clean the gummed up goo. I found that it got pretty wet from the cleaning but it does dry out with a paper towel or thin cotton rag. I think a Q tip might be helpful cleaning and drying in there too.