Thank Kokulan! That got me closer but now I'm getting the following exception:
The following errors were encountered while processing the workflow tree:
'DynamicActivity': The private implementation of activity '1: DynamicActivity' has the following validation error: Incorrect value specified for the 'ActivityType' property of the Interop activity 'CustomActivityStep16'. The value of this property must be a System.Type that inherits from System.Workflow.ComponentModel.Activity.
Unhandled exception:
Exception type: System.Activities.InvalidWorkflowException
Message: The following errors were encountered while processing the workflow tree:
'DynamicActivity': The private implementation of activity '1: DynamicActivity' has the following validation error: Incorrect value specified for the 'ActivityType' property of the Interop activity 'CustomActivityStep16'. The value of this property must be a System.Type that inherits from System.Workflow.ComponentModel.Activity.
at System.Activities.Hosting.WorkflowInstance.ValidateWorkflow(WorkflowInstanceExtensionManager extensionManager)
at System.Activities.Hosting.WorkflowInstance.RegisterExtensionManager(WorkflowInstanceExtensionManager extensionManager)
at System.Activities.WorkflowApplication.EnsureInitialized()
at System.Activities.WorkflowApplication.Enqueue(InstanceOperation operation, Boolean push)
at System.Activities.WorkflowApplication.InternalRun(TimeSpan timeout, Boolean isUserRun)
at System.Activities.WorkflowApplication.Run()
at Microsoft.Crm.Workflow.ActivityHost.StartWorkflowExecution(Activity workflow, ICommonWorkflowContext context)
at Microsoft.Crm.Workflow.ActivityHostBase.StartWorkflow(ICommonWorkflowContext context, Activity preLoadedActivity)
-- End stack trace --