Symptoms

Receiving the following error when trying to deploy a workflow with a start event (using SharePoint Remote Event Receiver).
“The "SourceCode.SharePoint15.DeploymentTask.Task" task failed unexpectedly.
System.Exception: Service: SharePointIntegration
Service Guid: 71810da1-81e2-4f22-8cf2-4011dacfdf42
Severity: Error
Error Message: Thread 1: Access denied. You do not have permission to perform this action or access this resource.

InnerException Message:

at SourceCode.SharePoint15.Utilities.Common.HandleSmartObjectException(SmartObjectException smartObjectException)
at SourceCode.SharePoint15.WorkflowIntegration.WorkflowIntegrationManager.RegisterRemoteEventReceivers(String siteURL, Guid listId, String eventReceiverTypes, String remoteEventReceiverURL)
at SourceCode.SharePoint15.DeploymentTask.Task.ExecuteInternal()
at SourceCode.SharePoint15.DeploymentTask.Task.Execute()
at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute()
at Microsoft.Build.BackEnd.TaskBuilder.d__26.MoveNext()”

The issue occurs for all sites within one site collection.
 

Diagnoses

The issue was caused by OAuth resource that the app was registered originally using a different account which is no longer valid.
 

Resolution

Perform the following steps resolved the issue.
1. Deleted the Resource for the oSite Collection] OAuth
(K2 Management > Authentication > OAuth > Resources
)
2. Went to App Activation and oSite Collection] was still and activated site and uninstalled it from the activated list.
3. Went back into App Activation and added Site Collection] to Activate
(App Catalog > K2 Appit for SharePoint)