Error: The server encountered an error processing the request. See server logs for more details

This issue comes into picture whenever there is any issue at WCF service.
 
So see more details about the issue, you need to includeExceptionDetailInFaults attribute to TRUE in serviceDebug tag.
 
 <serviceBehaviors>
         <behavior name="myServiceBehavior" >
           <serviceDebug includeExceptionDetailInFaults="true" />
         </behavior>
 </serviceBehaviors>
 
Either you can also add class attribute to the service class

Happy coding.. Hope this helps!