The subnet cannot be selected during CCN access.
The account of the CCN-associated VPC is different from that running the migration/sync task.
The account of the CCN-associated VPC must be the same as that running the migration/sync task.
For example, to migrate an instance from account A to account B, you should use account B to create a task, so the CCN-associated VPC must be under account B.
For more information on CCN configuration, see CCN Access: Configuring VPC-IDC Interconnection Through CCN.