This error is likely due to Amazon not having verified your additional services, such as RDS. Even though you may have an 'active account' (for example S3 works fine) that does not apply to all the sub-services that Amazon offers - you have to verify those separately by phone or email when you activate them.

Amazon uses various techniques to 'verify' you. You should have received an email with instructions to this effect, or alternatively there may be a verify button in the Amazon AWS dashboard for you to click on, which will give you a phone number to call.

Please contact Amazon for further assistance.