The .NET Extension Support mentioned above was the solution for me as well. I did not install the .NET Extension Support during the ArcGIS for Server install. To install go to control panel, programs and features, double click on the ArcGIS for Server, choose modify and install .NET Extension Support. Here is a good forum that explains it well. http://forums-old.arcgis.com/threads/94186-10.1-SOE-error-ClassFactory-cannot-supply-requested-class I also installed older versions of .NET Frame Works (versions 2, 3, 3.5 and 4). Problem: Could not publish a map services with SOE extension capabilities enabled. Errors I received: Packaging succeeded, but publishing failed. ERROR 001369: Failed to created service Can not open file C:\..., The system cannot find the path specified. Probable cause: The file is inaccessible to Server. ClassFactory Cannot supply requested class
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