Hi Mike, I was initially confused about why it sometimes didn't start to seal automatically when I put a bag edge in the slot. Turned it off and on, tried different things to no avail. It seems like you really have to leave the 4" of head room for it to turn on. Don't know what else it can be......let me know if you figure out an alternative answer. Checked trouble-shooting, etc. Also, definitely to seal the first edge of a roll bag you have to use the other button as directed in the manuel, otherwise you just have ongoing suction and no sealing since it's just sucking air through the other end of the open bag. Ahhhh, sometimes it pays to read the manual first. The good news is that their manual is pretty brief and easily read. Written by someone with English as a first language too!
I read somewhere on some review site that folks were having trouble with them not working after a while. Someone found that it was because the two seal gaskets (my name for them) rest on each other when it's not operating and they compress over time. They said to remove them, boil them and then reinstall after drying and thereafter keep something just behind the seal to keep the bars apart except when in use. Now....on my model I don't see removable seal gaskets but I'm being proactive on keeping them apart when no in use. I've used a bit of cardboard on each side where it hinges (there's a tiny area each side where there's no gasket) to keep the jaws apart.
Hope this helps and yes, if you figure anything out, please post it here!!!