This error indicates that the AWS cloud account is already protected by CloudGuard Dome9.
It can be by the CloudGuard Dome9 account you are currently trying to add this cloud account on ,or by another CloudGuard Dome9 account.
How to resolve this error
First verify on the Cloud Account page that you can find this cloud account.
If not, contact your system administrator to verify if there is another CloudGuard Dome9 account for the company.
This solution has been verified for the specific scenario, described by the combination of Product, Version and Symptoms. It may not work in other scenarios.