-snip-
I have my password.
I have my 18 word seed.
I have my Email nothing else.
I also want to know that have you used your wallet ID (available in the welcome message or maybe one of the first few messages from blockchain.com) as your username in the login field?
I think the issue is he's missing the 'Wallet ID' because he said "
nothing else" after the password and backup phrase.
So he can't try to login even if he wanted to.
Sorry to know that I thought that he is using his wallet ID and not getting to log in.
Then I think he have to go to email and have to get the wallet ID and to check once with wallet ID. As he is the older user of the older version maybe it will solve the issue.
Sometimes with after upgrade some issues and bugs are left in the software of any platform.