Why is my GP Web Service Extension not working?

I followed all the instructions at https://msdn.microsoft.com/en-us/library/cc508802.aspx

I edited the BusinessObjectsFile.config exactly as in the examples.

I had our partner copy both my extension DLL and BusinessObjectsFile.config to C:\Program Files\Microsoft Dynamics\GPWebServices

Our partner can not install remote debugging for reasons.

When I call the service, the extension data is not being returned.

There are no exception errors, no indication that anything went wrong. It is as if the web service host simply doesn't see the new extension. 

What is causing this?