I got 2 mT3's - 1 was DOA and the other is ok but definitely not my favorite tank.
Willing to bet your center post needs to be pulled down a touch. I have a dozen T3's, over 30 Kangers in total. Some need the post adjusted to contact the battery center pin, but NONE have ever been duds. No Kanger replacement wicks have EVER been duds in my purchases. YMMV
Op, what eliquid are you using? pg/vg blend?
Have you removed any flavor wicks?
Have you inspected the Wick coil Fit?
Wicks are hand assembled and can have alignment issues. Remove the base and look at the coil/wick from each side. There should be NO SPACE into the pipe around the wick. i.e. it must fill the gap. Fluff if needed or wiggle/pull the pipe over the wick off and inspect/correct to center all wicks(1 coiled, 2 flavor on top of coiled)
T3's rarely leak. Can happen but always a clear reason - once you understand tank function.
Also inspect tank for any sign of cracks. Air in = liquid out
