When you try to access the instance, you get a Bad Message
413 (Request Entity Too Large) error. This is a known Jenkins issue JENKINS-25046, specifically when using Jetty as the web server. As each time that Jenkins restarts its session cookie changes. The problem is that after some time, your browser can have a bunch of session cookies each one with a different name. This causes the cookie request header to be very long, this will cause the server to return a 413 response and a blank page.
In Jenkins versions higher than 2.66, you will have a Jetty version included that will allow you to customize the above described behavior via the following System properties:
executableWar.jetty.disableCustomSessionIdCookieNamethe default value for this property is false. You could set this to true to prevent the problem described above.
executableWar.jetty.sessionIdCookieNamewhich defaults to null. But sets a custom session ID cookie name when the previous parameter is set to false.