Mine's working great - but here's maybe some things that might be wrong, and maybe some questions that can lead to the solution.
Did you follow the instructions to flip the tank upside down before fully seating the top cap?
Might be some sort of O-Ring problem.
Maybe the atomizer was "dotted" too large so too much juice is getting in.
What type of eliquid are you using? Is it heavy on PG or VG?
What voltage are you vaping it at? Since it's a dual coil, maybe juice is coming in too fast to get vaporized, if the voltage isn't set high enough. I have a similar problem with cartos sometimes if I vape them too low - when I "pull" on the carto, it feeds in liquid through the holes in the carto, and if the voltage is set too low, it doesn't vaporize the eliquid fast enough.