What @Greg wanna explain was that when there is a new sentry, the node address has to be updated on persistent_peers of the validator node. Otherwise, the new sentry node won’t be useful as the validator node is not talking to the new sentry node.
He meant the validator node has to be restarted as the config.toml file was updated with the new sentry node address.
@Greg there is a way to avoid restarting the validator node which is to add the a new peer using the /dial_peers endpoint. @jack has mentioned about this in the following thread.