Symptoms

Whenever a user tries to deploy a workflow that has been created on a site registered with the K2 QA host server, the following error is raised: The "SourceCode.SharePoint15.DeploymentTask.Task" task failed unexpectedly.
System.Exception: Service: SharePointIntegration
Service Guid: 71810da1-81e2-4f22-8cf2-4011dacfdf42
Severity: Error
Error Message: OAuth token requires authorization.
 

Diagnoses

This is a result of the OAuth token becoming expired on the O365 environment for the Global Tenant Admin.
 

Resolution

Rerunning the registration wizard as Tenant Admin on sites where the error is being experienced seems to resolve the issue.