Based on what I'm hearing on the news, I'm guessing that the North Korean nuke did indeed fizzle. So now they know a few things: it's difficult to get the fissile material to build a nuke and now they've wasted some, it's damned expensive to test a nuke, doing it right is harder than they thought, and they don't have the expertise they thought they had. Everybody's mad at them now, and talking sanctions.
This would be an excellent time for them to save some face by demanding international aid in return for shutting down their nuclear weapons program and inviting international inspectors back in.