Having an issue upgrading your first Delivery Controller from XenApp 7.8 -> 7.9?

So encountered an issue with upgrading from XenApp 7.8 to 7.9. Install on upgrade of first 7.8 delivery controller to 7.9 goes fine until comes to the “Start the automatic Site upgrade” page. When clicking into it and perform site upgrade get greeted with a lovely:   “An unknown error occurred.   If the problem […]