Server not reachable: server version too low

use dashboard 5.3.0, server 6.4.0

app.use("/dashboard", dashboard);

server.start().then(function () {
    console.log("server start completed")
    app.use("/parse", server.app);
})

display in dashboard: Server not reachable: server version too low

when use use dashboard 5.3.0, server 5.6.0

app.use("/dashboard", dashboard);
app.use("/parse", server);

work fine. why ?