The thing is, this has probably been the issue with the last 5 boxes of cartos that I've used. I constantly have to keep "resetting" the brass screw :/
Once it's "reset" it starts working as normal until I put it in my pocket. I pull it out later, screw is still as snug as it was to start, but it won't fire until I reset it again. I guess it serves as some kind of off switch lock, but it definitely isn't normal imo.
what carto's you using? i have this problem with a kanger now and again. if it boges, i'de say ensure your brass screw is clean and free of corrosion, and also, wiggle that center pin of your carto out just a hair more. i go for center pin extending out past the negative terminal (or the threads)
also, is it just one tank? maybe not quite right tank that slipped through the cracks. >>> or more than one? tanks def seated all the way back? still not firing? maybe go the opposite direction, try closing the door, slappin it on your hand (door side down) then tightening. so it's actually offset a little and one side of the carto gets a strong contact with the brass. i do this last one often with my kangers.
my mistake in the learning curve with the billet box was focusing too much on the brass ring and not the positive contact on the bottom, if you can't resolve this brass ring issue, this might be what is it for you too. make sure the carto is down far enough past that little lip of platic on the tank, the one with the air holes. i was so hyper focused on the brass ring during some problems i forgot about that part.
hope some of this helps