The most common reason for this with a Kanger BCC is:
If you look at the bottom of a coil - not mounted in a base - there is the metal center post with a hole in it. That hole is how air gets into the coil assembly, over the coil and wick, and up through the vent tube to the mouth piece.
That center post is stuck into a silicone-ish grommet. (AKA: center post insulator.)
Ok, you mount the coil, do your thing filling the
tank etc. and then screw the PT onto your PV of choice. In some cases that center post insulator then gets compressed and squooshes flat. When that happens it blocks air from getting down the PT coil assembly that is supposed to get into that hole in the bottom of the center post. Screwing the PT onto the PV too tight definitely can cause the problem. In extreme cases the air flow is totally blocked when the PT is screwed onto a PV.
Take the PT off and pull the metal center post
straight out of the coil a tiny bit to decompress the center post insulator. DO NOT twist the center post or you risk breaking the legs off the coil. That slot in the center post is not a screwdriver adjustment slot.
Needless to say, avoid over-tightening the PT or it will happen again.