It may be your atomizer. I had the same problem with my M401 when I first got it. I was getting very little vapor. I tried dripping, changing carts, changing batteries, but no joy. I had purchased 2 kits and 2 spare atomizers, so I tried another atomizer. Same problem, very little vapor. Eventually I tried a 3rd atomizer and - boom! - huge clouds of vapor. It was odd that I got 2 bum attys in a row, but these things are made in China after all.

That's why I buy 2 kits at a time and spare parts when I get a new model. If you don't have any spare attys for your 510, order a couple of spares, preferably from a different supplier than you got your kit from (to try and get a different production run). Of course, you could just return the kit, but there's no guarrantee that a replacement would be any better and you may as well get used to buying spare parts. It's part of the deal if you use a PV. With all the new taxes, it's still cheaper than analogs.
BTW, I also have a 510, but I never had a problem with producing vapor. If the 510 has any flaw it is that it has to be topped off so often. It will really go through the juice!
TT33