If the battery is functioning properly and the e-cigarette does not want to fire, the battery may not contact the evaporator element (the coil). This contact is via the connection of the battery to the tank, so check first that the tank is properly on the battery. Check if there is no dirt or other debris between the tank and battery (even the actual contact point may become dirty).
If this also does not solve the problem, the chances are that the problem lies with the evaporating element, or the coil. It may be that the coil can not make good contact with the contact point of the tank. Remove the coil from the tank and take the inside of the tank (where the coil is attached) thoroughly. On the other hand, it may also be that the coil is broken internally, in this case you have to replace it.
If this does not help you can visit one of our stores so one of our experts can assist you.