A little bit of the "History of AttyPops' username"....
My 1st question or so on ECF was "My atty is making a loud popping sound...is the normal?" Not the usual hiss/sizzle... but a loud pop. I received the usual replies through the entire range of opinions. lol.
Anyway... the general consensus is that sometimes, with some atties, the little wicks inside go "pop" for some reason. There are several strands in there it it will usually still work if one pops.
I'm not sure what is going on with yours since you said "there is a faint quick hiss" but also said "there's no heat" (paraphrased).
Now... there are other things that can go wrong. Gunked coils can make it appear almost dead. If you're getting no heat whatsoever it's probably dead. Also CHECK that it is connecting properly... pry the little center post up on the connector with a paperclip and ensure that you are getting a good connection... sometimes they get pushed in. That's probably not it tho if you get hissing. Assuming that's not the issue... and cleaning it doesn't help, it's probably dead.
Dry dripping 2 drops directly into the atty, bypassing any carts and such. Maybe it just isn't wicking anything.
Not a bad idea to invest in an inexpensive multimeter to test atties with. You can verify the ohm rating for the atty, as well as check if they are dead.