Correct, Blockland keys can't just "break" they're either pirated from a keygen, someone else is using it, or you entered it wrong. Most likely you entered it wrong. Copy paste it from the email you got with the key in it.
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Nuff' said.
Sir, I don't know how to say this, so I'll try a way: Keygens work because a lot of programs are designed to auth while offline. And they also work because keys aren't up to a numbered system. All keys in Blockland are part of a numbered, registered system. You can't keygen Blockland because the key must be pre-created.
There won't be a keygen for BL. Since all keys are up with Badspot's database, and blah.
People getting his key... Perhaps. Entering it wrong might also be, but if this is how he asks, I think someone got his key.