PermissionDeniedException: ResourceIsMissing

I am receiving below error for only one mailbox when im trying to add users to that shared mailbox on portal. For other mailbox its working fine.

<RequestStatusDetail xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" DetailLevel="Information" EntryTime="2016-02-06T17:20:29.4982645Z">Microsoft.ResourceManagement.WebServices.Exceptions.PermissionDeniedException: ResourceIsMissing
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.ExecuteGetAction(RequestType request)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.ExecuteAction(RequestType request)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.ExecuteAction[ResponseBodyType](RequestType request)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.DispatchRequest[ResponseBodyType](RequestType request, Guid requestIdentifier, Object redispatchSingleInstanceKey, Boolean isRedispatch)
   at Microsoft.ResourceManagement.WebServices.RequestDispatcher.DispatchRequest[ResponseBodyType](RequestType request)
   at Microsoft.ResourceManagement.Workflow.Hosting.RequestWorkItemProcessor.DispatchRequest[TResponseType](RequestType request, Boolean applyAuthorizationPolicy)
   at Microsoft.ResourceManagement.Workflow.Hosting.RequestWorkItemProcessor.ProcessGetWorkItem(ReadRequestWorkItem readWorkItem)
   at Microsoft.ResourceManagement.Workflow.Hosting.RequestWorkItemProcessor.ProcessWorkItem(WorkItem workItem)</RequestStatusDetail>