I mean something had to wrong versus the inside envelope.
The outside of the envelope has all your personal information: name, DOB, address, reason for voting provisionally, etc.. Inside the sealed envelope is your ballot. If the outside doesn't pass muster, for example, you are not registered at all in a state that requires pre-election day registration, then the envelope is never even opened and the ballot inside it is never even seen.
Provisional ballots can prevent a lot of mess-ups for people who think that they have registered, but whose name is not on the list in the precinct where they show up to vote. If you vote provisionally in a precinct not your own, then the local election races are not counted; only those that are common to both precincts, like US Senator.