Any log messages? Even if you don't see any, you might have to knock the logging level down to Info level.
IIS restart might help as well... as well as investigating the setup of the app in IIS (app pool user, authentication level, etc).
Maybe inspecting the IIS logs to see if the service is even attempting to be invoked (for example, if the service is being his but theres a HTTP error code, its an IIS/authentication thing)