Business process error on a Real-time Workflow

Hello community,

I am facing to an issue on a real-time workflow.  The log is th following :

Sync workflow failed with error message - Unhandled Exception: Microsoft.Crm.Workflow.Services.InvalidCustomActivityExecutionException: System.ServiceModel.Security.SecurityNegotiationException: Microsoft Dynamics CRM has experienced an error. Reference number for administrators or support: #FA57B4E3
   at System.Activities.WorkflowApplication.Invoke(Activity activity, IDictionary`2 inputs, WorkflowInstanceExtensionManager extensions, TimeSpan timeout)
   at System.Activities.WorkflowInvoker.Invoke(Activity workflow, IDictionary`2 inputs, TimeSpan timeout, WorkflowInstanceExtensionManager extensions)
   at Microsoft.Crm.Workflow.SynchronousRuntime.SynchronousWorkflowActivityHost.ExecuteWorkflowUsingInvoker(Activity workflow, ICommonWorkflowContext context)
  at Microsoft.Crm.Workflow.SynchronousRuntime.SynchronousWorkflowActivityHost.StartWorkflow(WorkflowActivationData activationData, ICommonWorkflowContext context)
, error code - -2147220891

Some ideas for helping me ?

Thanks in advance

Thanks in advanceThT