Cannot create unknown type

Problem

The orders will not start and the error below is thrown in the Workflow Manager eventlog.

Source: Workflow Manager

WorkflowSessionConfigurationFailedException was swallowed at location DispatchLoopInstanceAsyncResult.Isolate. Microsoft.Activities.Dispatcher.WorkflowSessionConfigurationFailedException ---> System.Xaml.XamlObjectWriterException: Cannot create unknown type '{clr-namespace:Zipper.ZervicePoint.ProcessSystem.Activities;assembly=Zipper.ZervicePoint.ProcessSystem.Activities}SetOrderRunningState'.
   at System.Xaml.XamlObjectWriter.WriteStartObject(XamlType xamlType)
   at System.Xaml.XamlServices.Transform(XamlReader xamlReader, XamlWriter xamlWriter, Boolean closeWriter)
   at System.Activities.XamlIntegration.FuncFactory`1.Evaluate()
   at System.Activities.DynamicActivity.OnInternalCacheMetadata(Boolean createEmptyBindings)
   at System.Activities.Activity.InternalCacheMetadata(Boolean createEmptyBindings, IList`1& validationErrors)
   at System.Activities.ActivityUtilities.ProcessActivity(ChildActivity childActivity, ChildActivity& nextActivity, Stack`1& activitiesRemaining, ActivityCallStack parentChain, IList`1& validationErrors, ProcessActivityTreeOptions options, ProcessActivityCallback callback)
   at System.Activities.ActivityUtilities.ProcessActivityTreeCore(ChildActivity currentActivity, ActivityCallStack parentChain, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList`1& validationErrors)
   at System.Activities.ActivityUtilities.CacheRootMetadata(Activity activity, LocationReferenceEnvironment hostEnvironment, ProcessActivityTreeOptions options, ProcessActivityCallback callback, IList`1& validationErrors)
   at System.Activities.Hosting.WorkflowInstance.ValidateWorkflow(WorkflowInstanceExtensionManager extensionManager)
   at System.Activities.Hosting.WorkflowInstance.RegisterExtensionManager(WorkflowInstanceExtensionManager extensionManager)
   at Microsoft.Activities.Hosting.HostedWorkflowInstance.RegisterExtensions(IEnumerable`1 extensions)
   at Microsoft.Activities.Hosting.WorkflowSession.ConfigureEnvironment(Activity workflowDefinition, IWorkflowConfiguration workflowConfiguration, IEnumerable`1 hostExtensions)
   at Microsoft.Activities.Dispatcher.DispatchLoopInstanceAsyncResult.ConfigureWorkflowSessionEnvironment(MessageSessionContext messageSession, WorkflowSession workflowSession, Activity rootActivity, IWorkflowConfiguration workflowConfiguration)

Solution

The Workflow Manager Extension is not properly installed on the system. You can verify this by checking the following folder:

C:\Program Files\Workflow Manager\1.0\Workflow\Artifacts

The following files should exist in this folder:

• Zipper.ZervicePoint.ProcessSystem.Activities.dll
• Zipper.ZervicePoint.ProcessSystem.Commands.dll
• Zipper.ZervicePoint.ProcessSystem.Messaging.dll
• v8-ia32.dll
• v8-x64.dll
• ClearScript.dll
• ClearScriptV8-32.dll
• ClearScriptV8-64.dll

The solution is to make sure the Workflow Manager Extension is installed by running the installer again, making sure this component is checked on the initial screen.

Note: The installer does more than copying these files to this folder.