I have a 12-word mnemonic from a Blockchain.info wallet created in May 2013. But now the Blockchain recovery page[1] 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I'm wondering if the standards have changed since 2013 and the type of seed I got is no longer valid?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?