I got this strange error from the WCF-WebHttp sending a payload to a web service bound to a receive location.

The adapter “WCF-WebHttp” raised an error message. Details “System.IO.FileNotFoundException: The system cannot find the file specified. (Exception from HRESULT: 0x80070002)
at Microsoft.BizTalk.Adapter.Wcf.Runtime.BizTalkServiceInstance.EndOperation(IAsyncResult result)
at AsyncInvokeEndEndTwoWayMethod(Object , Object[] , IAsyncResult )
at System.ServiceModel.Dispatcher.AsyncMethodInvoker.InvokeEnd(Object instance, Object[]& outputs, IAsyncResult result)
at System.ServiceModel.Dispatcher.DispatchOperationRuntime.InvokeEnd(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.ImmutableDispatchRuntime.ProcessMessage7(MessageRpc& rpc)
at System.ServiceModel.Dispatcher.MessageRpc.Process(Boolean isOperationContextSet)”.

Tried varies things such as restarting hosts, IIS and also looked at this post BizTalk WebHttp – Error 404 with RESTful Receive Port (which re-registers IIS .net).  But my solution was the standard Windows one, a restart of the server and things worked again.