I would call PCL on Monday morning after 6 am PT. This may be an account issue they can fix for you. You may have several accounts, that they need to merge. Never try to link accounts or bookings and never register after you have an account.
Try signing in with your name, dob and booking number, not your user name and Password. Or, to see your current booking, use the downloaded App instead.
Askoceanmedallion@carnival.com
Sounds like a corrupt account
Name
Ship and sail date
Booking number
Explain in Subject field:
Account Access Denied Help!
If you just show the sail date, it will be a long time, they work by date of travel.