Hey SkiSki, you can certainly have a second subscription using your other mobile service.
If you try to register again does it give you an error message?
Have you tried to reset the password for the second number?
Because it's one email on one Optus account covering two mobile phones. When I enter my email for the 2nd mobile, it states, already registered. I tried another one of my emails and it didn't accept it because it's not attached to the account
Hmm that unusual, you can only have one email address per subscription so you'd need a second one for the second mobile service.
When you entered the code and added the new email address what error message did you get when you get?