Might have a flooded atty or simple gunked up.
1st thing to do is take your atty off and blow it out. If a lot of juice comes out then your flooding it. Very possible with certain cart mods or even if they arnt just right..
If its not flooded it may just need to be cleaned out. This is what I do every few nights and I'm getting pretty consistent vapage.
1 - flush your atty under tap hot water for about 30 seconds or so (you don't need to boil it or make baths with weird stuff for ages, just flush it with hot water for 30 seconds)
2 - blow with your mouth through boths ends (big hole/little hole) of the atty for few seconds to just let it dry a little.
3 - connect your atty to your PV (a regular 3.7v device or ecig) without the cart or cart filler (!!) and perform a 12 seconds (cut-off) dry burn (press the button till cut-off while gently blowing through the mouthpiece -801- or empty cart -510/901- be sure you're blowing -not draggin inside-
you will see a little vapor coming out (it's vaporized water).
If you do not blow while dry burning the coil may get TOO HOT and you may damage it.
4 - do this dry burn 4 times in a row. After that your atty will be perfectly dry and ready to get new juice again.
5 - drip between 5 to 8 drops of liquid into the atty (801), or 2 to 5 (510).
wait a least 2 seconds between any drop, the mesh needs to absorb each drop before adding another one.
Or you might just have a dead atty worst case scenario
How long have you had it yer cig?
But like captjay said driping ive found is the best route. Very VERY stupid to do while driving, but luckily I have a 20 min drive to work so I load up b4.