Adding an ArcIMS service to ArcMap by clicking a GND file on a web page does not work consistently if ArcMap is not already open. If ArcMap is not open, clicking a GND file should always launch ArcMap and add the service. This is affecting many portal and clearinghouse websites where ArcIMS services are accessed by clicking on GND files
You can start ArcMap first before clicking on any link in a web page that says 'Add To ArcMap' or similar.Alternately, if you are comfortable editing the windows registry, you can change the following reg key:HKEY_CLASSES_ROOT\GeographyNetwork.Document\shell\open\command from this: <a href="file:C:/arcgis/Bin/ArcMap.exe" target="_blank">C:\arcgis\Bin\ArcMap.exe</a> /dde(where <a href="file:C:/arcgis/Bin/ArcMap.exe" target="_blank">C:\arcgis\Bin\ArcMap.exe</a> is the path to the location of your ArcMap.exe)to this:<a href="file:C:/arcgis/Bin/ArcMap.exe" target="_blank">C:\arcgis\Bin\ArcMap.exe</a> /dde Open("%1") by adding Open("%1") to the end