How to get cell values to update properly

Dashboard.java

    @FXML public TableView<ServerInstance> _serverTable;
    @FXML public TableColumn<ServerInstance, Number> _smtpPort;
    @FXML public TableColumn<ServerInstance, Number> _popPort;
    @FXML public TableColumn<ServerInstance, Number> _messageCount;
    @FXML public TableColumn<ServerInstance, Number> _receivedCount;

// ...

    @Override
    @SuppressWarnings("unused")
    public void initialize(URL location, ResourceBundle resources) {
        _servers = FXCollections.observableList(new ArrayList<>());
        _serverTable.setItems(_servers);
        _smtpPort.setCellValueFactory(param -> param.getValue().getSmtpPort());
        _popPort.setCellValueFactory(param -> param.getValue().getPopPort());
        _messageCount.setCellValueFactory(param -> param.getValue().getMessageCount());
        _receivedCount.setCellValueFactory(param -> param.getValue().getTotalReceived());
// ...
    }


/* And then, in ServerInstance: */
    private SimpleIntegerProperty _smtpPort = new SimpleIntegerProperty();
// ...
    @SuppressWarnings("unused")
    public ObservableValue<Number> getSmtpPort() {
        return _smtpPort;
    }