Issues must be assigned

Symptoms

An issue does not get synchronized, and it appears on the troubleshooting screen with the category 'Issue must be assigned' and the message 'assignee:Issue must be assigned'.

Cause

This error is probably caused because the 'allow unassigned issues' setting in JIRA is set to OFF.

Resolution

You can fix this problem in two ways:

1. Enable unassigned issues in JIRA (this will also allow the target issue to be unassigned)
   
   
2. In the Backbone configuration, edit the 'assignee' field, and check 'Ignore empty values for this user field'. In this case, syncing from a issue with no assignee to an issue with an assignee will not remove the assignee in the target issue.