Earlier quoted context omitted.
It's failed if Coinbase suspected fraud and it's reversed.
From their Terms of Service: > 3.5 When buying or selling bitcoin, you are buying or selling from Coinbase directly. Coinbase does not act as an intermediary or marketplace between other buyers and sellers of bitcoin.
That's fine that they can reverse transactions that are fraud. However after investigating the transaction and determining that it isn't fraud, then they should be on the hook for honoring the transaction. Incorrectly flagging legitimate transactions as fraudulent is their problem, not the customer's. They should either improve the algorithm or provide additional controls that give them confidence that a transaction is not fraudulent (e.g. two factor authentication. linking bank accounts and confirming a person's identity). If a person has completed all the security requirements Coinbase has, then that person should be able to make a transaction with the confidence actually will clear.