Symptoms

 An event inside of the workflow (K2 Studio) that generates a PDF from a URL which used to work fine stopped working - you are getting a blank form with the following error message message:

ID4243: Could not create a SecurityToken. A token was not found in the token cache and no cookie was found in the context.
 

Diagnoses

Error message suggests that authentication is failing due to a session cookie being stored in the cache. By default both token expiration settings are set to 8 hours. Given that the form is opening within the workflow and not by a user this is not very clear how/why the session is expiring.

We restarted the K2Blackpearl service and the PDF is generating again but how can we prevent the error happening again?

It seems that restart of the K2 service is required.
 

Resolution 

Restart K2 Service.