java.lang.Exception: java.io.IOException: Server object extension '<name of server extension>' not found

Error Message

Sometimes when performing edits or using geoporcessing tools on a service the following error may be returned:

Error handling schema request: java.lang.Exception: java.io.IOException: Server object extension 'utilitynetworkserver' not found., Internal server error.

This error can show up in ArcGIS Pro, mobile applications such as Field Maps, and in ArcGIS Server logs.

Note: 
The bold section of the message above, "utilitynetworkserver",  can refer to any of the listed service capabilities. The solution provided is the same for each respective capability.

Cause

This is due to the listed service capability not being selected in ArcGIS Server Manager. While the error says "Server object extension", this does not correlate to SOEs in Server Manager > Extensions. 

For example, in this error, we see that it references the Utility Network Server. If we navigate to Server Manager, click on the service, and select Capabilities, note that under the "Select and configure capabilities" heading, Utility Network is not checked, as shown in the image below.

This can be further be confirmed by clicking the associated service capability and checking the REST URL under the respective Configuration heading. If the REST URL hyperlink is not active, as shown in the next image, the capability is not applied.

Solution or Workaround

1. To resolve the problem, in ArcGIS Server Manager, under Capabilities > Select and configure capabilities, select (check) the server capability listed in the error message. In this example, it is the Utility Network capability.
2. Click Save and Restart.
   • If you click the aforementioned service capability to open the Configuration heading, note that the REST URL hyperlink is active, as shown in the following image.

Note:
This workflow does not work with the Version Management capability. This option cannot be changed once a service is published. This option must be checked in ArcGIS Pro before publishing to use this capability.