“The default account is not initialized” error is displayed when adding an IAM role to Veeam Backup for AWS

1. Make sure the backup server (EC2 instance where Veeam Backup for AWS is installed) has internet access to the required AWS services. For more information, see this AWS article. Make sure all endpoints for the required AWS services are reachable from the backup server. For more information on service endpoints and quotas for AWS services, see the AWS General Reference guide.
2. Connect to the backup server with the following command:

ssh -i "<backup server's .pem key>" ubuntu@<Public DNS (IPv4) parameter of the backup server>

3. Restart the Veeam Backup for AWS service running on the backup server with the following command:

sudo systemctl restart veeamawsbackup.service

The Default Backup Restore IAM role should be created automatically after you perform these steps.