I think this error occurs because you are trying to reset a non-persistent task: http://developer.axonivy.com/doc/latest/DesignerGuideHtml/ivy.concepts.html#ivy-wf-states
You can for the task to be persistent immediately when a user starts a process: See the Start-Element reference http://developer.axonivy.com/doc/latest/DesignerGuideHtml/ivy.processmodeling.html#ivy-processmodels-elements-startrequest
![alt text][2]
![alt text][1]
[1]: http://answers.axonivy.com/upfiles/startDocExtract.pnghttp://answers.axonivy.com/upfiles/startDocExtract.png
[2]: http://answers.axonivy.com/upfiles/persistOnCreation_inscription.png
