Hi lukeragno,
I've tested your code and couldn't detect the problem. It works fine to me. I recorded the video here: http://recordit.co/MrzQxy3BD0
PS: After debug Max's code, I found a problem is the custom post type was registered too early, before all the "init" hook, where Meta Box starts. So, that's might be the problem. I recommend checking the code again, make sure it looks like
add_action( 'init', 'my_register_post_type' );