DH email can be… Problematic.
However, one thing I’ve found out after multiple chats on the topic is that new accounts or changes to passwords can sometimes take up to 2 hours to begin working. When you talk to chat, they are probably doing whatever the delayed script would be doing.
The on-screen notice you get will tell you “up to 15 minutes” but it would seem that isn’t accurate anymore.
If you’ve done either of those actions, give it a few hours before attempting to login.