for the life of me I cant figure out how to get anything with a 510 to work on this. For that matter a 801 or 901. What am I missing here??? Nothing fits. I cant even get it on. Its like the threads where the pin is, isnt made right. I am totally confused. I feel like Im just starting out vaping again. I feel like an idiot to ask this but dont know what else to do. Could I be missing a part?