Buy a new plan and renew your existing plan is not the same.
If you purchase a new plan, the system will assign you a new service port number, a new service password, and the original server node configuration. You will need to redo a node subscription to update your service node configuration.
If you choose to renew your existing plan, only your existing plan capacity, traffic restriction, and the plan expirary date will be changed, while the service port number, password and service node configuration remain the same.