Had the same problem on the istick 30. My RDA non adjustable center positive pin was overly recessed in one of my RDA's. All other RDA's had an exposed or protruding pin profile and worked perfectly when attached directly to the istick.
Your istick probably came with a Ego Adapter with an adjustable 510 to 510 center pin, mine did.
Re:
Eleaf 510 to eGo Thread Adapter (Connector) by iSmoka
I placed the above adapter on the 30 istick and no fire. Adjusted the center pin on the adapter and got intermittent firing (RDA+adapter+30). I found the adapter pin could not be adjusted far enough to make contact with the 30 reliably.
To allow the recessed RDA center pin to screw in closer the center pin, I filed down the top (4ea. 1/16" slot barre sidel) circular surface between adapter and RDA. I removed approx. 1/16" height of adapter. This permitted the RDA (all other RDA's too) and adapter to function/fire consistently.
Cons:
This adapter add an extra 1/2" to the over all height of the 30.
Advantages:
I can get my fat fingers on my RDA bottom casing and quickly remove the cap if I wish to.
My 30 which has stainless steel harden threads will be doubly guarded against wear. Ismoka Eleaf realize that when two metal surfaces work against each other in screwing back and forth, the softer metal will be worn. Hence, a loose thread (created from metal degrading through wear) equals no contact/firing of topper.
The above adapter is a sacrificial goat to prevent a 30 (any mod) female threads from being worn by constant use.
The Ismoka Eleaf 510 - Ego Adapter I use is a brass base material coated with decorative thin chrome (no real wear resistant plating).
Re:
Keep Stripping Mod Threads | E-Cigarette Forum