If you are getting this message "Authorizing your account to access Amazon S3 service" in Amazon S3 after signup, then this is what you might have missed. Check if you have subscribed to Amazon S3 service after you registered an AWS account.
“You need to do both: register for an AWS account and subscribe for Amazon S3 service”.
So let's review the steps you followed to create an account and subscribe for S3 services.
How to create a new Account on Amazon S3
and make sure that you followed the correct way; hopefully this will solve the problem.
- A User Interface for Amazon S3
to explore Amazon S3 buckets, once your account has been authorized .