Issues related to the host addresses authorized by the account: The database account has restricted the access to specific host addresses.
Please make sure you have authorized all IPs accessing the DMC server in this region within the host restriction of the account you are logging into. For details about how to authorize IPs, please refer to Modifying Host Addresses with Access Permissions. Alternatively, you can directly use '%' to allow all IPs and only use the security group to limit the origin of database access.