An issue does not get synchronized and appears in the troubleshooting section with the category 'Epic is not accessible' and the message, e.g. 'You do not have the permission to view the linked epic:'PROJZ-1''.
Backbone is configured to synchronize Epic links into a text field, but the sync user lacks access to the linked Epic in the synchronized issue.
Following is an example scenario:
Suppose ticket P-1 is being synchronized from Project A to Project B.
There exists an Epic with key E-1, which is present in a different project: Project E.
The sync user hasn't been granted the necessary permissions to access Project E.
When linking E-1 to the epic link field of the issue P-1, backbone might throw this error.
Grant the synchronization user the necessary permissions to the project where the epic exists.
The sync user is part of the project role 'atlassian-addons-project-access'.
Perform a resync against the error in the troubleshooting tab and the error should be resolved if appropriate permissions were granted.
You do not have the permission to view the linked epic: XXXXX
Browse projects: for the project where the epic exists