Could be that
juice has gotten into the battery, which is a pretty serious thing. Cartomizers were meant to be disposable, and with refilling comes a certain amount of caution.
Last resort is that you just need to blow into the battery end (without a cartomizer on). Outside of that, I am tapped. You might need to ask for a replacement.
If that's the case, using shortie manuals is your best bet...they won't fail on you with refilling or using blanks.