Scenario 1: External Load Balancer or DNS Round-Robin
An external load balancer or DNS Round-Robin has been configured between the tenant's environment and the Cloud Connect Provider's Cloud Gateways, which causes traffic to be sent to a Cloud Gateway other than the one assigned to the tenant's task.
As each task begins on the tenant's side of the connection, the Cloud Connect server creates a dedicated traffic forwarding rule for the backup traffic. This traffic rule is based on Veeam Cloud Connects internal load-balancer selecting the Cloud Gateway server with the least amount of tasks already assigned. Once the traffic rule is created, that tenant's backup activity is expected to use the designated Cloud Gateway and is not allowed to use any gateways where this rule does not exist.
An external load balancer or DNS Round-Robin breaks this logic and may cause tenant traffic bound to a specific forwarding rule to be sent to a different Cloud Gateway, resulting in the error mentioned above.
Here is an example of how that incorrect configuration will appear within the view in the Veeam Cloud Connect Console: