Connectivity issues

If you've used different model e-cigs and mods for even a short period of time, you're bound to have come across connectivity issues. By their very design, e-cig parts usually have moveable connectors so that parts of different heights can properly meet each other. Unfortunately, this sometimes leads to the exact opposite situation, particularly when you've been using one type of part, and then switch to another, you might find that the first part has depressed the centre pole connection in your battery so that it won't now meet the centre pole of the new part.

Here's a page that explains this phenomenon a little better, and offers a couple of tips too:

Inside a 510 Connector