Steps to Replicate

• On a fresh installation of JIRA 6.0.3 and GreenHopper 6.2.4.1*, we create a new board:
  

• Create a Scrum board:
  

• Board from an existing project:
  

• Include the board name and the project(s):
  

• After that, create a new Epic:
  

• Confirm that the Epic is created:
  

• Click on the dropdown of the Epic and choose View in JIRA:
  

• Close the Epic from the JIRA view issue screen:
  

• Proceed with the process:
  

• Confirm that the Epic is in the Closed status:
  

• Go back to the Scrum board and click on the dropdown menu for the Epic. Choose Mark as Done:
  

• Confirm on the process:
  

• The following Error will be displayed:
  

This can be quite confusing since we have to ensure either:

• When the Epic is closed on JIRA's side, the Epic should also be closed on the Scrum board

OR

• Allow Epic closure only for Scrum Board side, not JIRA

Also tested on GreenHopper 6.2.4 and GreenHopper 6.2.3