IIS issues - blank page

I’m transferring my setup to some new servers. Basically, getting rid of WAMP (only used for apache & PHP; MySQL was already on a different server) and using IIS. I’ve seen posts here where it should work, and am confident that it would work as well.

However:
Lot’s off issues when I try to get a new instance up and running, no idea why.
Moved my existing setup (recreated database, copied all the files) towards my new environment (Windows Server 2012 r2, running PHP 5.6.x now in IIS, 7.2.9 gave issues on the useage of the each() function apparently), changed url & database settings.
Got as far as I do get a HTTP 200 back from the webserver and no error is logged anywhere (not in the application logs, nor in the PHP logs), but I just get an empty page as result.

Anyone an idea on how to solve?

Many thanks!

edit: am on 1.5.5 still, once I got this issue solved, I will start the upgrade (unless there is proof that I just should do this on my old environment and make the switch after that)

Can’t assist here as I don’t have access to any server with IIS installed.

If you want, I can provide a virtual harddisk, ready with a draft deployment (invoiceplane on IIS & MySQL DB)?
Would take a day or so to create and a bit to upload for you (would be about 7.5GB).
Would that help?
(Note, it will be a 180 evaluation license)

You can temporarily turn on error display.

In the web root directory, open the index.php file in an editor and add the following lines

error_reporting(E_ALL);
ini_set('display_errors', TRUE); 

Your file should look like this

<?php

error_reporting(E_ALL);
ini_set('display_errors', TRUE); 

/**
 * DO NOT EDIT THIS FILE!
 * Make a copy of the ipconfig.php.example file, rename the copy to 'ipconfig.php' and set your settings in this file
 */

/*
 *---------------------------------------------------------------
 * LOAD DOTENV
 *---------------------------------------------------------------
 */
      // .......
     // ..........