Geocoding service “Address locator “ fails to work in Geocortex

Despite the fact that the Geocoding service “Address locator “ is working at the Arcgis desktop and Arcgis Server level, it fails to work in geocortex environment.

/customer/servlet/servlet.FileDownload?file=00P6000000elzGtEAI

/customer/servlet/servlet.FileDownload?file=00P6000000elthHEAQ

/customer/servlet/servlet.FileDownload?file=00P6000000em1WbEAI

Software versions

Geocortex Essentials 4.2.1 / Geocortex viewer for Silverlight 2.3.1

ArcGIS Desktop 10.2.2 / ArcGIS Server 10.2.2

What might be the issue here ?

Many thanks, any help is greatly appreciated.