Try these steps:
1. Make sure that the LED light at the end of the battery is lighting up when you take a puff
2. If yes, then go to step 3. If no, then it is most likely a dead battery. Charge battery and try again. If still no light, probably a broken battery.
3. The atomizer may be flooded. Try unscrewing the battery, and blowing
through the end of the atomizer that faces the battery and out towards the end that faces the cartridge ( hope that makes
sense). Try to get all of the liquid out, without getting any spit inside.
4. Clean the brass connectors on both the battery and atomizer. Screw the atomizer back into the battery, and insert a new or freshly refilled cartridge into the atomizer. If there is still no vapor, then it is most likely a dead atomizer.