Invoke RESTful Web Service Failed with ISG_UNKNOWN_SERVICE

Hi Experts,

I'm trying to invoke one fnd_user_pkg API using Restful web services on EBS 12.2.5. The deploy and grant are all successful. But when I invoke the WADL by REST client, it errors out:

{

"ISGServiceFault" : {

  "Code" : "ISG_UNKNOWN_SERVICE",

  "Message" : "Requested web service does not exist",

  "Resolution" : "Requested web service or web resource does not exist or it is undeployed, please deploy it.",

  "ServiceDetails" : {

  "ServiceName" : "testusername",

  "OperationName" : "",

  "InstanceId" : "0"

  }

}

}

Is there anything I missed? I'm not sure what the problem is since it's deployed fine.

Any input is appreciated.