I have a 12-word mnemonic from a Blockchain.info wallet created in May 2013. But now the Blockchain recovery page tells me this is an invalid seed.
I'm sure this is not user error, since the recovery phrase was found in two different places: backed up in a file on S3, and printed on a piece of paper.
I also tried the Blockchain app as well as Mycelium, and got the same result.
I'm wondering if the standards have changed since 2013 and the type of seed I got is no longer valid? Is there a tool I can try to feed this mnemonic into so I can generate the wallet?