Application returning Error with possible port communication issue

Sorry, I was on my iPhone so previous answer is a bit short.

Fiddler runs as a proxy. So you will be able to see and examine in detail any traffic that is passed. Because it acts as a MITM it will decode your TLS and let you see the content. Easily identifying the actual content and request that is timing out. From that you can work out if it's a missing VS (i.e. your app uses multiple ports and you've only configured one) or it's not being rewritten correctly (i.e. embedded URL's in the content aren't being changed from the backend IP:port to the VS ip:port)

More info on fiddler is available at http://www.telerik.com/fiddler