There are a great many clients claiming that their blockchain.info wallet cant login successfully. their 12 words recovery phrase not work. locked due to the second password and showing error of “failed to upgrade HD and save wallet”
This problem mainly happens in mid 2016. this is caused by the internal bug of blockchain.info wallet. their legacy wallet conflict with the HD wallet. for those who did not set 2nd password will failed to upgrade to HD timely. this error cant be fixed automatically by blockchain.info/ blockchain.com. that is why they are get locked out for many years still unresolved. the 12 words recovery phrase does not work as they are for the HD wallet in your wallet and they dont control the legacy wallet in your old wallet. Now all blockchain wallets only provide the HD wallet, causing the problem unresolved and their support cant help as they cant degrade their new wallets to the old wallets years ago.
however, there is still high chance to recover if you have necessary info/data. like: Wallet ID, correct passwords/hints; access to the email used for blockchain wallet, wallet.aes.json, etc. you dont need all of these info. but you need action fast to reach us because we need gain data from their website if you dont have the original wallet.aes.json. while this approach not work all the time. please store your btc in core wallet after succeed.